ARM: socfpga_defconfig: Add back DEBUG_FS

Commit 0e4a459f ("tracing: Remove unnecessary DEBUG_FS dependency")
removed select for DEBUG_FS but we still need it for development purposes.

Fixes: 0e4a459f ("tracing: Remove unnecessary DEBUG_FS dependency")
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

arch/arm/configs/socfpga_defconfig

@@ -157,6 +157,7 @@ CONFIG_NLS_ISO8859_1=y
 CONFIG_PRINTK_TIME=y
 CONFIG_DEBUG_INFO=y
 CONFIG_MAGIC_SYSRQ=y
+CONFIG_DEBUG_FS=y
 CONFIG_DETECT_HUNG_TASK=y
 # CONFIG_SCHED_DEBUG is not set
 CONFIG_FUNCTION_TRACER=y