posix_types.h: Cleanup stale __NFDBITS and related definitions

Recently, glibc made a change to suppress sign-conversion warnings in
FD_SET (glibc commit ceb9e56b3d1).  This uncovered an issue with the
kernel's definition of __NFDBITS if applications #include
<linux/types.h> after including <sys/select.h>.  A build failure would
be seen when passing the -Werror=sign-compare and -D_FORTIFY_SOURCE=2
flags to gcc.

It was suggested that the kernel should either match the glibc
definition of __NFDBITS or remove that entirely.  The current in-kernel
uses of __NFDBITS can be replaced with BITS_PER_LONG, and there are no
uses of the related __FDELT and __FDMASK defines.  Given that, we'll
continue the cleanup that was started with commit 8b3d1cda4f
("posix_types: Remove fd_set macros") and drop the remaining unused
macros.

Additionally, linux/time.h has similar macros defined that expand to
nothing so we'll remove those at the same time.

Reported-by: Jeff Law <[email protected]>
Suggested-by: Linus Torvalds <[email protected]>
CC: <[email protected]>
Signed-off-by: Josh Boyer <[email protected]>
[ .. and fix up whitespace as per akpm ]
Signed-off-by: Linus Torvalds <[email protected]>

security/selinux/hooks.c

@@ -2129,7 +2129,7 @@ static inline void flush_unauthorized_files(const struct cred *cred,
 		int fd;
 
 		j++;
-		i = j * __NFDBITS;
+		i = j * BITS_PER_LONG;
 		fdt = files_fdtable(files);
 		if (i >= fdt->max_fds)
 			break;