fsmap.h: add linux/fsmap.h to UAPI compile-test coverage

linux/fsmap.h is currently excluded from the UAPI compile-test because
of the error like follows:

    HDRTEST usr/include/linux/fsmap.h
  In file included from <command-line>:
  ./usr/include/linux/fsmap.h:72:19: error: unknown type name ‘size_t’
     72 | static __inline__ size_t
        |                   ^~~~~~

The error can be fixed by replacing size_t with __kernel_size_t.

Then, remove the no-header-test entry from user/include/Makefile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/uapi/linux/fsmap.h

@@ -69,7 +69,7 @@ struct fsmap_head {
 };
 
 /* Size of an fsmap_head with room for nr records. */
-static inline size_t
+static inline __kernel_size_t
 fsmap_sizeof(
 	unsigned int	nr)
 {

usr/include/Makefile

@@ -26,7 +26,6 @@ no-header-test += linux/am437x-vpfe.h
 no-header-test += linux/coda.h
 no-header-test += linux/cyclades.h
 no-header-test += linux/errqueue.h
-no-header-test += linux/fsmap.h
 no-header-test += linux/hdlc/ioctl.h
 no-header-test += linux/ivtv.h
 no-header-test += linux/kexec.h