kernel: remove CONFIG_ZONE_DMA_FLAG from 4.9

There are no CONFIG_ZONE_DMA_FLAG config symbol since 4.7.

Signed-off-by: Sergey Ryazanov <[email protected]>

target/linux/generic/config-4.9

@@ -5266,7 +5266,6 @@ CONFIG_XZ_DEC=y
 # CONFIG_ZLIB_DEFLATE is not set
 # CONFIG_ZLIB_INFLATE is not set
 CONFIG_ZONE_DMA=y
-CONFIG_ZONE_DMA_FLAG=1
 # CONFIG_ZPA2326 is not set
 # CONFIG_ZPOOL is not set
 # CONFIG_ZRAM is not set