initramfs: Fix initramfs size for 32-bit arches

Commit ffe8018c3424 ("initramfs: fix initramfs size calculation") broke
32-bit big-endian arches like (on ARAnyM):

VFS: Cannot open root device "hda1" or unknown-block(3,1)
Please append a correct "root=" boot option; here are the available partitions:
fe80 1059408 nfhd8 (driver?)
fe81 921600 nfhd8p1 00000000-0000-0000-0000-000000000nfhd8p1
fe82 137807 nfhd8p2 00000000-0000-0000-0000-000000000nfhd8p2
0200 3280 fd0 (driver?)
0201 3280 fd1 (driver?)
0300 1059408 hda driver: ide-gd
0301 921600 hda1 00000000-0000-0000-0000-000000000hda1
0302 137807 hda2 00000000-0000-0000-0000-000000000hda2
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(3,1)

As pointed out by Kerstin Jonsson <kerstin.jonsson@ericsson.com>, this
is due to CONFIG_32BIT not being defined, so the initramfs size field is
done as a 64-bit quad. On little-endian (like x86) this doesn matter,
but on a big-endian machine the 32-bit reads will see the (zero) high
bits.

Only mips, s390, and score set CONFIG_32BIT for 32-bit builds, so fix it for
all other 32-bit arches by inverting the logic and testing for CONFIG_64BIT,
which should be defined on all 64-bit arches.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
[ I think we should just make it "u64" on all architectures and get
rid of the whole #ifdef CONFIG_xxBIT - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>