powerpc: Fix dedotify for binutils >= 2.26

Since binutils 2.26 BFD is doing suffix merging on STRTAB sections.  But
dedotify modifies the symbol names in place, which can also modify
unrelated symbols with a name that matches a suffix of a dotted name.  To
remove the leading dot of a symbol name we can just increment the pointer
into the STRTAB section instead.

Backport to all stables to avoid breakage when people update their
binutils - mpe.

Cc: stable@vger.kernel.org
Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

(backported from commit f15838e9)
BugLink: http://bugs.launchpad.net/bugs/1557130Signed-off-by: Andy Whitcroft <apw@canonical.com>

arch/powerpc/kernel/module_64.c

@@ -335,7 +335,7 @@ static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
 		if (syms[i].st_shndx == SHN_UNDEF) {
 			char *name = strtab + syms[i].st_name;
 			if (name[0] == '.')
-				memmove(name, name+1, strlen(name));
+				syms[i].st_name++;
 		}
 	}
 }