MIPS: BCM47XX: Select SYS_SUPPORTS_HIGHMEM for BCM47XX_BCMA

It seems that bcm47xx can handle only 128 MiB of RAM directly. There
are few devices with 256 MiB, but Broadcom's SDK uses highmem to handle
anything above 128 MiB.
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/7101/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/bcm47xx/Kconfig

@@ -20,6 +20,7 @@ config BCM47XX_SSB
 config BCM47XX_BCMA
 	bool "BCMA Support for Broadcom BCM47XX"
 	select SYS_HAS_CPU_MIPS32_R2
+	select SYS_SUPPORTS_HIGHMEM
 	select CPU_MIPSR2_IRQ_VI
 	select BCMA
 	select BCMA_HOST_SOC