ARM: socfpga_defconfig: enable FS configs to support Angstrom filesystem

systemd on the Angstrom root file system expects AUTOFS to be configured
as a module and NFSD to be statically linked into the kernel. This patch
adds the necessary configuration to get rid two "FAILED" error messages
during systemd startup.

Signed-off-by: Matthew Gerlach <mgerlach@opensource.altera.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
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v2: provide a more descriptive changelog