msm: camera: vfe: Avoid subscribing to IRQ for slave core

In dual IFE case, bus IRQs from slave VFE core should
be ignored. This change adds a check for dual IFE and
master/slave core to proceed with subscribing for IRQs.

Change-Id: I86ecda5f51611f9a4ac912f3bd0ebe96aded5a98
Signed-off-by: Venkat Chinta <vchinta@codeaurora.org>