media: uapi: Add meta formats for PiSP FE config and stats

Add two meta formats for PiSP FE: V4L2_META_FMT_RPI_FE_CFG and
V4L2_META_FMT_RPI_FE_STATS. The former is used to provide configuration
for the FE and the latter is used to read the statistics from the FE.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>