s390/sysinfo: convert bogomips calculation to C

Provide several one instruction fpu inline assemebles and use them to
implement the bogomips calculation in C like style. This is more for
illustration purposes on how kernel fpu code can be written in C.

This has the advantage that the author only has to take care of the
floating point instructions, but doesn't need to take care of general
purpose register allocation (if needed), and the semantics of all other
instructions not related to fpu.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>