mfd: rc5t583: Fix warning messages

Two variables named master_int and sleepseq_val, were just
declared without initialization. Pointers to these variables
were passed to mfd read function. After that these variables
were used for some of the logical operations.

Though logically there is nothing wrong, compiler is complaining
that the variables may be used uninitialized.

Hence fixing these warning messages by initializing them.

Signed-off-by: Venu Byravarasu <vbyravarasu@nvidia.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>