msm: msm_sdcc: Rename dfab_clk to generic name

dfab_clk is used to vote for SDCC AHB clock derived
from Dayatona fabric. This naming convention is invalid
for targets where the AHB clocks are derived from other
buses like peripheral NoC. Hence, rename this to a generic
name that is applicable for all targets.

Change-Id: I9563342f07430cc000c86a93d265ff126003c8a5
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>