msm: generalize clock support.

The 'PCOM' method of clock control (commands issued to the radio
CPU) is shared across several (but not all) Qualcomm SOCs.
Generalize this clock mechanism so these other SOCs can be added.

Signed-off-by: Gregory Bean <gbean@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Daniel Walker <dwalker@codeaurora.org>
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>