ARM: brcmstb: select ARCH_DMA_ADDR_T_64BIT for LPAE

Broadcom STB (BRCMSTB) has some 64-bit capable DMA and therefore needs
dma_addr_t to be a 64-bit size.  One user is the Broadcom SATA3 AHCI
controller driver.

Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Olof Johansson <olof@lixom.net>