[ARM] 3963/1: AT91: Update configuration files

A number of configuration file changes.

These are mainly to replace references to ARCH_AT91RM9200 and
ARCH_AT91SAM9261 with the common/generic ARCH_AT91.  That way we don't
need to mention every specific AT91 processor explicitly.

Also adds the configuration option for AT91SAM9260-EK and AT91SAM9261-EK
boards.

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