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 <law@redhat.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
CC: <stable@vger.kernel.org>
Signed-off-by: Josh Boyer <jwboyer@redhat.com>
[ .. and fix up whitespace as per akpm ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/select.c

@@ -345,8 +345,8 @@ static int max_select_fd(unsigned long n, fd_set_bits *fds)
 	struct fdtable *fdt;
 
 	/* handle last in-complete long-word first */
-	set = ~(~0UL << (n & (__NFDBITS-1)));
-	n /= __NFDBITS;
+	set = ~(~0UL << (n & (BITS_PER_LONG-1)));
+	n /= BITS_PER_LONG;
 	fdt = files_fdtable(current->files);
 	open_fds = fdt->open_fds + n;
 	max = 0;
@@ -373,7 +373,7 @@ get_max:
 			max++;
 			set >>= 1;
 		} while (set);
-		max += n * __NFDBITS;
+		max += n * BITS_PER_LONG;
 	}
 
 	return max;
@@ -435,11 +435,11 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 			in = *inp++; out = *outp++; ex = *exp++;
 			all_bits = in | out | ex;
 			if (all_bits == 0) {
-				i += __NFDBITS;
+				i += BITS_PER_LONG;
 				continue;
 			}
 
-			for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
+			for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
 				int fput_needed;
 				if (i >= n)
 					break;