kvmtool: Fix compile error on MIPS

When including asm-generic/types.h instead of asm/types.h it results
in conflicting types for __s64 et al (at least with my
toolchain). Other header files are including asm/types.h
(e.g. include/kvm/ioport.h) and types defined there don't necessarily
match the types defined in asm-generic/types.h.

Signed-off-by: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>