ARM: gic: Refactor code for gic_configure_and_raise

Currently the offset and bit calculation in the function was
hardcoded for IPC1 interrupt. To support other secondary cores
we have to refactor the code to calculate the offset and bits
as per the cpu and interrupt number.

Change-Id: I33de8f185c219fb6a8e9d7f9676e958f27d54a12
Signed-off-by: Taniya Das <tdas@codeaurora.org>