MIPS: malta: memory.c: Initialize the 'memsize' variable

MIPS: malta: memory.c: Initialize the 'memsize' variable

If the 'memsize' environmental variable is not set by the bootloader
the 'memsize' variable is not initialized, leading to potential memory
problems. This patch fixes the problem by setting the initial
value to '0' to force the kernel to set a good default memory size.

Cc: <stable@vger.kernel.org> # v3.15+
Reported-by: Matheus Almeida <Matheus.Almeida@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/6984/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>