uapi: Introduce capture rate and CVP frame rate controls

Introduce V4L2_CID_MPEG_VIDC_CAPTURE_FRAME_RATE and
V4L2_CID_MPEG_VIDC_CVP_FRAME_RATE controls to indicate capture
frame rate and cvp frame rate respectively. Capture rate and CVP
frame rate are needed in deriving CVP skip ratio. While encoding
frames, firmware uses CVP skip ratio to scale CVP metadata from
earlier frames.

Change-Id: Iede53da9c31c2e7d187d1542903e6c8e2ed0979b
Signed-off-by: Akshata Sahukar <asahukar@codeaurora.org>