drivers: edac: Allow IRQ line to be shared

Other drivers in the kernel might want to use
the same interrupt line that is used for llcc
edac. Allow the interrupt line to be shared with
other drivers by marking the line as shared at the
time of request, and modify IRQ handler to identify
if the interrupt is meant to be handled by edac or
not.

Change-Id: Ic06cf44540689d0f629607907bb9985fabe4cbaf
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>