power: smb1398: Fix array index out of bounds error

In smb1398_get_irq_index_byname() while accessing 'smb_irqs' we
may cause array index out of bound error. Fix this by looping
till ARRAY_SIZE(smb_irqs) instead of NUM_IRQS.

While at it also fix usage of uninitialized variable of 'main_fcc_ua'.

Change-Id: I2f726cdc23fdbff431d48699c8407744dd0ca93e
Signed-off-by: Ashish Chavan <ashichav@codeaurora.org>