msm: kgsl: get pm_qos_latency from device tree

pm_qos_latency parameter can be configured from
device tree as well. Will set to default value if
entry not found in target device tree.

Conflicts:
	include/linux/msm_kgsl.h

Change-Id: I76271f4fdc26e191431e5dfe2a6de9e2b3ab426f
Signed-off-by: Prakash Kamliya <pkamliya@codeaurora.org>
msm: kgsl: change pm_qos_latency to pm-qos-latency

Use hyphen symbol instead of underscore for pm-qos-latency
property name. Hyphen should be used instead of underscore
in device tree property name.

Change-Id: I23f720159b4ecb3d81cbd13b570cee8fc633253a
Signed-off-by: Prakash Kamliya <pkamliya@codeaurora.org>