scripts/kernel-doc: recognize __meminit

Fix scripts/kernel-doc to recognize __meminit in a function prototype
and to strip it, as done with many other attributes.

Fixes this warning:

  Warning(..//mm/page_alloc.c:2973): cannot understand function prototype: 'void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask) '
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/kernel-doc

@@ -2085,6 +2085,7 @@ sub dump_function($$) {
     $prototype =~ s/^noinline +//;
     $prototype =~ s/__init +//;
     $prototype =~ s/__init_or_module +//;
+    $prototype =~ s/__meminit +//;
     $prototype =~ s/__must_check +//;
     $prototype =~ s/__weak +//;
     my $define = $prototype =~ s/^#\s*define\s+//; #ak added