MIPS: delay.c: Check BITS_PER_LONG instead of __SIZEOF_LONG__

MIPS: delay.c: Check BITS_PER_LONG instead of __SIZEOF_LONG__

When building a 32-bit kernel for RBTX4927 with gcc version 4.1.2 20061115
(prerelease) (Ubuntu 4.1.1-21), I get:

arch/mips/lib/delay.c:24:5: warning: "__SIZEOF_LONG__" is not defined

As a consequence, __delay() always uses the 64-bit "dsubu" instruction.

Replace the check for "__SIZEOF_LONG__ == 4" by "BITS_PER_LONG == 32" to
fix this.

Introduced by commit 5210edcd527773c227465ad18e416a894966324f [MIPS: Make
__{,n,u}delay declarations match definitions and generic delay.h"]

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Patchwork: https://patchwork.linux-mips.org/patch/4678/
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>