crc32: use uint32_t rather than unsigned long

The envcrc.c does sizeof(unsigned long) when calculating the crc, but
this is done with the build toolchain instead of the target tool
chain, so if the build is a 64bit system but the target is 32bits,
the size will obviously be wrong. This converts all unsigned long
stuff related to crc32 to uint32_t types. Compile tested only: output
of ./tools/envcrc when run on a 32bit build system matches that of a
64bit build system.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>