drivers: mfd: Reset register values to 0 if core in power collapse

Reset the register value array to "0" when register
read is performed while digital core is in power collapse.

Change-Id: Ieb835b81639f906f20a1f749c1458c3973c2c4e0
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>