malta: enable HighMem on MIPS32

It allows to use more than 256MB memory on MIPS32.

Signed-off-by: Aleksander Jan Bajkowski <[email protected]>

target/linux/malta/be/config-default

@@ -1,3 +1,4 @@
 CONFIG_CPU_BIG_ENDIAN=y
 # CONFIG_CPU_LITTLE_ENDIAN is not set
 CONFIG_CPU_MIPS32_R2=y
+CONFIG_HIGHMEM=y

target/linux/malta/le/config-default

@@ -1,3 +1,4 @@
 # CONFIG_CPU_BIG_ENDIAN is not set
 CONFIG_CPU_LITTLE_ENDIAN=y
 CONFIG_CPU_MIPS32_R2=y
+CONFIG_HIGHMEM=y