msm: kgsl: Add new sysfs node to list GPU clock frequencies

Add a new sysfs node to communicate available GPU clock frequencies
to userspace for the power daemons.

Signed-off-by: Anshuman Dani <adani@codeaurora.org>
(cherry picked from commit 0e80b365d2b6e15344a774667a1e273edb2d64ff)

Conflicts:

	drivers/gpu/msm/kgsl_pwrctrl.c

Signed-off-by: Sridhar Gujje <sgujje@codeaurora.org>
(cherry picked from commit 9ca738c3c746017e5a4c8d5fe64e1ed3e6128cc1)

Change-Id: I623a36148ae86a9a527f28e7d768535f67ceaa01
Signed-off-by: Sridhar Gujje <sgujje@codeaurora.org>