scripts/kernel-doc: fix fatal script error

Fix fatal error in scripts/kernel-doc by ignoring the "__weak" attribute:

  Error(drivers/pci/pci.c:2820): cannot understand prototype: 'char * __weak pcibios_setup(char *str) '
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/kernel-doc

@@ -1786,6 +1786,7 @@ sub dump_function($$) {
     $prototype =~ s/__init +//;
     $prototype =~ s/__init_or_module +//;
     $prototype =~ s/__must_check +//;
+    $prototype =~ s/__weak +//;
     $prototype =~ s/^#\s*define\s+//; #ak added
     $prototype =~ s/__attribute__\s*\(\([a-z,]*\)\)//;