unicore32: Use Kbuild infrastructure for kvm_para.h

All the headers but kvm_para.h use the Kbuild infrastructure to
get to the asm-generic headers.

Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>