ARM: dts: at91: Don't build unnecessary dtbs

Building both ARMv4 and ARMv5 dtbs when SOC_SAM_V4_V5 is an issue for
kernelci because it will then attempt to boot ARMv4 kernels on at91sam9
which doesn't work.

Use CONFIG_SOC_AT91RM9200 and CONFIG_SOC_AT91SAM9 instead.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>