ARM: 9260/1: lib/xor: use r10 rather than r7 in xor_arm4regs_{2|3}

kbuild test robot reports:
In file included from crypto/xor.c:17:
./arch/arm/include/asm/xor.h:61:3: error: write to reserved register 'R7'
                GET_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:20:10: note: expanded from macro 'GET_BLOCK_4'
        __asm__("ldmia  %0, {%1, %2, %3, %4}"
                ^
./arch/arm/include/asm/xor.h:63:3: error: write to reserved register 'R7'
                PUT_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:42:23: note: expanded from macro 'PUT_BLOCK_4'
        __asm__ __volatile__("stmia     %0!, {%2, %3, %4, %5}"
                             ^
./arch/arm/include/asm/xor.h:83:3: error: write to reserved register 'R7'
                GET_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:20:10: note: expanded from macro 'GET_BLOCK_4'
        __asm__("ldmia  %0, {%1, %2, %3, %4}"
                ^
./arch/arm/include/asm/xor.h:86:3: error: write to reserved register 'R7'
                PUT_BLOCK_4(p1);
                ^
./arch/arm/include/asm/xor.h:42:23: note: expanded from macro 'PUT_BLOCK_4'
        __asm__ __volatile__("stmia     %0!, {%2, %3, %4, %5}"
                             ^
Thumb2 uses r7 rather than r11 as the frame pointer. Let's use r10
rather than r7 for these temporaries.

Link: ClangBuiltLinux#1732
Link: https://lore.kernel.org/llvm/[email protected]/

Reported-by: kernel test robot <[email protected]>
Suggested-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Signed-off-by: Russell King (Oracle) <[email protected]>

arch/arm/include/asm/xor.h

@@ -51,7 +51,7 @@ xor_arm4regs_2(unsigned long bytes, unsigned long * __restrict p1,
 	register unsigned int a1 __asm__("r4");
 	register unsigned int a2 __asm__("r5");
 	register unsigned int a3 __asm__("r6");
-	register unsigned int a4 __asm__("r7");
+	register unsigned int a4 __asm__("r10");
 	register unsigned int b1 __asm__("r8");
 	register unsigned int b2 __asm__("r9");
 	register unsigned int b3 __asm__("ip");
@@ -73,7 +73,7 @@ xor_arm4regs_3(unsigned long bytes, unsigned long * __restrict p1,
 	register unsigned int a1 __asm__("r4");
 	register unsigned int a2 __asm__("r5");
 	register unsigned int a3 __asm__("r6");
-	register unsigned int a4 __asm__("r7");
+	register unsigned int a4 __asm__("r10");
 	register unsigned int b1 __asm__("r8");
 	register unsigned int b2 __asm__("r9");
 	register unsigned int b3 __asm__("ip");