driver/mutex: disable preemption in enter and enter_common

We can't use smp_processor_id() from preemptible code, and such a
bug will be generated by the kernel (in DEBUG):

BUG: using smp_processor_id() in preemptible [00000000] code: bash/4268

This is only a small patch, that did this only for mutex, there too many
places where there is also smp_processor_id() used.
driver/proc: add compat functions only if kernel < 2.6.25

I remember that Paul, wrote he made a fix by him self, but I also need
this, so I fixed it by myself.
Merge branch 'preemptible-kernel' into unofficial-master