ARM: dts: msm: Add regulator to enable clock for sdm845

Add top_gdsc regulator to enable the mclk, correct the
one of the csiphy clock source for sdm845.

CRs-Fixed: 2015567
Change-Id: Ib11ca98a7de1f87609d8fb25c9732cf26eb19aff
Signed-off-by: Viswanadha Raju Thotakura <viswanad@codeaurora.org>