[ARM] 4656/1: AT91: Tweak interrupt priorities

Slight tweaking of the default interrupt priorities (AIC) for the
integrated peripherals on the AT91RM9200, AT91SAM9260, AT91SAM9261 and
AT91SAM9263 processors.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>