i2c: Allow selecting BCM2835 I2C controllers on ARCH_BRCMSTB

ARCH_BRCMSTB platforms have the BCM2835 I2C controllers, allow
selecting the i2c-bcm2835 driver on such platforms.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>