kernel: add missing config symbol

Signed-off-by: Felix Fietkau <[email protected]>

target/linux/generic/config-4.4

@@ -1093,6 +1093,7 @@ CONFIG_FAT_DEFAULT_IOCHARSET="iso8859-1"
 # CONFIG_FB_NEOMAGIC is not set
 # CONFIG_FB_NVIDIA is not set
 # CONFIG_FB_OF is not set
+# CONFIG_FB_OMAP2 is not set
 # CONFIG_FB_OPENCORES is not set
 # CONFIG_FB_PM2 is not set
 # CONFIG_FB_PM3 is not set