Revert "genirq: Provide an accessor for IRQ_PER_CPU flag"

This reverts commit 2868c034. An upstream
patch, providing the same functionality, has been added, allowing this
commit to be removed.

Change-Id: I1ae50c0efb1ef560c8a3ff257fada3edfaf328ea
Signed-off-by: Ian Maund <imaund@codeaurora.org>