libkmod-elf: Fix check by class in get_modversions()

Commit 51c409b ("Cache the offset of crc") unintentinally changed the
comparison "if (elf->class & KMOD_ELF_32)" to
"if (elf->class == KMOD_ELF_32)".

This has been reported by Serge Voilokov <serge0x76@gmail.com>:

	On Raspberry PI elf->class equals KMOD_ELF_32|KMOD_ELF_LSB so
	valid condition should be (elf->class & KMOD_ELF_32) instead of
	(elf->class == KMOD_ELF_32).

This fixes "modprobe --dump-modversions" failing on 32b systems.