irqchip: atmel-aic-common: Prevent clobbering of priority when changing IRQ type

This patch makes the bitmask for AIC_SRCTYPE consistent
with that of its valid values, and prevents the priority
field at bits 2:0 from being clobbered by an incorrect
AND with the AIC_SRCTYPE mask.

Signed-off-by: Gavin Li <gavinli@thegavinli.com>
Cc: <stable@vger.kernel.org> # v3.17+
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Link: https://lkml.kernel.org/r/1420598843-8409-1-git-send-email-gavinli@thegavinli.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>