[S390] Bogomips calculation for 64 bit.

The bogomips calculation triggered via reading from /proc/cpuinfo
can return incorrect values if the qrnnd assembly is called with a
pointer in %r2 with any of the upper 32 bits set.
Fix this by using 64 bit division / remainder operation provided by
gcc instead of calling the assembly.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>