drivers: arm-smmu: Add clock support for QCOM_SMMUV2

The QCOM_SMMUV2 is an implementation of the arm,smmu-v2 architecture.
The qcom,smmu is instantiated for each of the multimedia cores (for eg)
Venus (video encoder/decoder), mdp (display) etc, and they are connected
to the Multimedia Aggregator Interconnect (MMAGIC). So the access to
any of the MMU's registers, as well as MMU's downstream bus access,
requires the specified MMAGIC clocks to be enabled. So adding a new
binding for the qcom,smmu-v2 and the required mmagic clock bindings for
the same. Also adding the support for enabling the qcom,smmu-v2 clocks in
the driver.

               -------------  ---------
               |   VENUS   |  | MDP   |
	       |	   |  |       |
	       -------------  --------
		     |           |
		     |           |
                  ------      ---------
                  |SMMU |     | SMMU  |
                  |	|     |       |
                  ------      --------
		    |            |
		    |            |
       -----------------------------------------
       |	MMAGIC INTERCONNECT (MMSS NOC) |
       |                                       |
       -----------------------------------------
                   |                 |
		   |           ----------------------------------
                 -----         | 	SYSTEM NOC		|
                 |DDR|	       |				|
                 -----         ---------------------------------
		   |		    |
                   |               ------
		   |<-------------| CPU|
				  ------

Signed-off-by: Sricharan R <sricharan@codeaurora.org>