ARC: [lib] strchr breakage in Big-endian configuration

For a search buffer, 2 byte aligned, strchr() was returning pointer
outside of buffer (buf - 1)

------------->8----------------
    // Input buffer (default 4 byte aigned)
    char *buffer = "1AA_";

    // actual search start (to mimick 2 byte alignment)
    char *current_line = &(buffer[2]);

    // Character to search for
    char c = 'A';

    char *c_pos = strchr(current_line, c);

    printf("%s\n", c_pos) --> 'AA_' as oppose to 'A_'
------------->8----------------

Reported-by: Anton Kolesov <[email protected]>
Debugged-by: Anton Kolesov <[email protected]>
Cc: <[email protected]> # [3.9 and 3.10]
Cc: Noam Camus <[email protected]>
Signed-off-by: Joern Rennecke  <[email protected]>
Signed-off-by: Vineet Gupta <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/arc/lib/strchr-700.S

@@ -39,9 +39,18 @@ ARC_ENTRY strchr
 	ld.a	r2,[r0,4]
 	sub	r12,r6,r7
 	bic	r12,r12,r6
+#ifdef __LITTLE_ENDIAN__
 	and	r7,r12,r4
 	breq	r7,0,.Loop ; For speed, we want this branch to be unaligned.
 	b	.Lfound_char ; Likewise this one.
+#else
+	and	r12,r12,r4
+	breq	r12,0,.Loop ; For speed, we want this branch to be unaligned.
+	lsr_s	r12,r12,7
+	bic 	r2,r7,r6
+	b.d	.Lfound_char_b
+	and_s	r2,r2,r12
+#endif
 ; /* We require this code address to be unaligned for speed...  */
 .Laligned:
 	ld_s	r2,[r0]
@@ -95,6 +104,7 @@ ARC_ENTRY strchr
 	lsr	r7,r7,7
 
 	bic	r2,r7,r6
+.Lfound_char_b:
 	norm	r2,r2
 	sub_s	r0,r0,4
 	asr_s	r2,r2,3