media: hantro: fix kernel-doc warnings and style

media: hantro: fix kernel-doc warnings and style

Add a description for enum values in hantro_enc_fmt,
in order to fix these warnings:

drivers/staging/media/hantro/hantro_hw.h:149: warning: Enum value 'RK3288_VPU_ENC_FMT_YUV420P' not described in enum 'hantro_enc_fmt'
drivers/staging/media/hantro/hantro_hw.h:149: warning: Enum value 'RK3288_VPU_ENC_FMT_YUV420SP' not described in enum 'hantro_enc_fmt'
drivers/staging/media/hantro/hantro_hw.h:149: warning: Enum value 'RK3288_VPU_ENC_FMT_YUYV422' not described in enum 'hantro_enc_fmt'
drivers/staging/media/hantro/hantro_hw.h:149: warning: Enum value 'RK3288_VPU_ENC_FMT_UYVY422' not described in enum 'hantro_enc_fmt'

While here, improve the kernel-doc style, adding an empty
line before the fields of the structs.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>