x86: efi: Fix EFI 64-bit payload build warnings

x86: efi: Fix EFI 64-bit payload build warnings

There are lots of warnings when building EFI 64-bit payload.

include/asm-generic/bitops/__fls.h:17:2:
  warning: left shift count >= width of type
  	if (!(word & (~0ul << 32))) {
			^

In fact, U-Boot itself as EFI payload is running in 32-bit mode.
So BITS_PER_LONG needs to still be 32, but EFI status codes are
64-bit when booting from 64-bit EFI. Introduce EFI_BITS_PER_LONG
to bridge those status codes with U-Boot's BITS_PER_LONG.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>