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>

arch/powerpc/kernel/module_64.c

@@ -340,7 +340,7 @@ static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
 			if (name[0] == '.') {
 				if (strcmp(name+1, "TOC.") == 0)
 					syms[i].st_shndx = SHN_ABS;
-				memmove(name, name+1, strlen(name));
+				syms[i].st_name++;
 			}
 		}
 	}