ARM: socfpga_defconfig: Enable CONFIG_MTD_ALTERA_SYSMGR

Add System Manager driver by default for SOCFPGA ARM32 platforms.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>