media: tvp541x: fix some kernel-doc parameters

Solve the following warnings:
  + drivers/media/i2c/tvp514x.c: warning: Excess function parameter 'a' description in 'tvp514x_g_frame_interval':  => 759
  + drivers/media/i2c/tvp514x.c: warning: Excess function parameter 'a' description in 'tvp514x_s_frame_interval':  => 784
  + drivers/media/i2c/tvp514x.c: warning: Function parameter or member 'ival' not described in 'tvp514x_g_frame_interval':  => 759
  + drivers/media/i2c/tvp514x.c: warning: Function parameter or member 'ival' not described in 'tvp514x_s_frame_interval':  => 784

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>