[ARM] 4478/1: AT91: Convert AT91RM9200 to use atmel_spi driver

Convert the AT91RM9200 platform-setup code to use the new atmel_spi
driver (and manually-driven chip-selects), instead of the legacy
AT91-only SPI stack.

The AT91SAM9 processors are already using the atmel_spi driver.

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