asoc: wcd937x: Clear Buck disable flag in PMU even if already up

Buck disable flag, which is used to indicate if suspend can disable
the buck, is not cleared during powerup if it is already enabled.
This causes suspend to disable buck even during active usecase.
Clear the buck disable flag when returning due to already enable.

Change-Id: I5118b66492dff27965a587e1bc6b916d5c26b9fb
Signed-off-by: Ramprasad Katkam <katkam@codeaurora.org>