cnss2: Use command DB name from device tree

The command DB name which indicates the PMIC rail used for open loop
CPR feature should come from device tree since in different platforms,
it may use different PMIC rail.

Change-Id: Ia5b62cec5e1fefd8ed019524215a4ad2c9048c2c
Signed-off-by: Yue Ma <yuem@codeaurora.org>