malta: Allow MIPS64 builds

Both real Malta boards & emulators that mimic Malta (eg. QEMU) can
support MIPS64 CPUs. Allow MIPS64 builds of U-Boot for such boards,
which enables the user to make use of the whole 64 bit address space.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 53363e3..abaeaf0 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -33,6 +33,9 @@
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select SUPPORTS_CPU_MIPS32_R6
+	select SUPPORTS_CPU_MIPS64_R1
+	select SUPPORTS_CPU_MIPS64_R2
+	select SUPPORTS_CPU_MIPS64_R6
 	select SWAP_IO_SPACE
 	select MIPS_L1_CACHE_SHIFT_6