initramfs: fix clang build failure

There is only one function in init/initramfs.c that is in the .text
section, and it is marked __weak.  When building with clang-12 and the
integrated assembler, this leads to a bug with recordmcount:

  ./scripts/recordmcount  "init/initramfs.o"
  Cannot find symbol for section 2: .text.
  init/initramfs.o: failed

I'm not quite sure what exactly goes wrong, but I notice that this
function is only ever called from an __init function, and normally
inlined.  Marking it __init as well is clearly correct and it leads to
recordmcount no longer complaining.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnd Bergmann <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Barret Rhoden <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

init/initramfs.c

@@ -535,7 +535,7 @@ extern unsigned long __initramfs_size;
 #include <linux/initrd.h>
 #include <linux/kexec.h>
 
-void __weak free_initrd_mem(unsigned long start, unsigned long end)
+void __weak __init free_initrd_mem(unsigned long start, unsigned long end)
 {
 #ifdef CONFIG_ARCH_KEEP_MEMBLOCK
 	unsigned long aligned_start = ALIGN_DOWN(start, PAGE_SIZE);