buildid: reduce header file dependencies for module

The vmlinux decompressor code intentionally has only a limited set of
included header files, but this started running into a build failure
because of the bitmap logic needing linux/errno.h:

In file included from include/linux/cpumask.h:12,
                 from include/linux/mm_types_task.h:14,
                 from include/linux/mm_types.h:5,
                 from include/linux/buildid.h:5,
                 from include/linux/module.h:14,
                 from arch/arm/boot/compressed/../../../../lib/lz4/lz4_decompress.c:39,
                 from arch/arm/boot/compressed/../../../../lib/decompress_unlz4.c:10,
                 from arch/arm/boot/compressed/decompress.c:60:
include/linux/bitmap.h: In function 'bitmap_allocate_region':
include/linux/bitmap.h:527:25: error: 'EBUSY' undeclared (first use in this function)
  527 |                 return -EBUSY;
      |                         ^~~~~
include/linux/bitmap.h:527:25: note: each undeclared identifier is reported only once for each function it appears in
include/linux/bitmap.h: In function 'bitmap_find_free_region':
include/linux/bitmap.h:554:17: error: 'ENOMEM' undeclared (first use in this function)
  554 |         return -ENOMEM;
      |                 ^~~~~~

This is easily avoided by changing linux/buildid.h to no longer depend on
linux/mm_types.h, a header that pulls in a huge number of indirect dependencies.

Fixes: b9c957f554442 ("bitmap: move bitmap_*_region() functions to bitmap.h")
Fixes: bd7525da ("bpf: Move stack_map_get_build_id into lib")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

include/linux/buildid.h

@@ -2,10 +2,11 @@
 #ifndef _LINUX_BUILDID_H
 #define _LINUX_BUILDID_H
 
-#include <linux/mm_types.h>
+#include <linux/types.h>
 
 #define BUILD_ID_SIZE_MAX 20
 
+struct vm_area_struct;
 int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
 		   __u32 *size);
 int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);