ARM: dts: msm: Add sw_reset register support to GPU_GX GDSC on MSMCOBALT

In order to flush out the demet cells in the GFX PMIC domain,
the GFX SW reset should be asserted and de-asserted before
enabling the gdsc_gpu_gx. Add the sw_reset DT property for
the GDSC. Also, correct mapping the domain_addr register to
gdsc_gpu_gx instead of gdsc_gpu_cx.

Change-Id: I1f60e764f8f62e7e4e1be66f1917c1a7ef71fa41
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>