ARM: omap2plus_defconfig: Add back DEBUG_FS

Commit 0e4a459f56 ("tracing: Remove unnecessary DEBUG_FS dependency")
removed select for DEBUG_FS but we still need it at least for enabling
deeper idle states for the SoCs.

Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/configs/omap2plus_defconfig

@@ -556,5 +556,6 @@ CONFIG_DEBUG_INFO=y
 CONFIG_DEBUG_INFO_SPLIT=y
 CONFIG_DEBUG_INFO_DWARF4=y
 CONFIG_MAGIC_SYSRQ=y
+CONFIG_DEBUG_FS=y
 CONFIG_SCHEDSTATS=y
 # CONFIG_DEBUG_BUGVERBOSE is not set