[S390] Have param.h simply include <asm-generic/param.h>.

Since the files have identical content, might as well simplify.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>