crypto: ice: Fix NULL pointer exception in ice.

While enabling ICE setup and on error conditions, the regulator
is disabled. Before disabling the regulator, check if the
regulator is up and able to access the registers of regulator.

Change-Id: I94dd2b3e25444818f7bdf2f791f4fa9efaefce15
Signed-off-by: Brahmaji K <bkomma@codeaurora.org>