ARM: socfpga_defconfig: Add back DEBUG_FS
Commit 0e4a459f56c3 ("tracing: Remove unnecessary DEBUG_FS dependency")
removed select for DEBUG_FS but we still need it for development purposes.
Fixes: 0e4a459f56c3 ("tracing: Remove unnecessary DEBUG_FS dependency")
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>