media: imx: imx7_mipi_csis: Inline mipi_csis_set_hsync_settle()

The mipi_csis_set_hsync_settle() is small, called from a single place,
and misnamed (HS stands for high speed, not horizontal sync). Inline it
in its only caller, and refactor the HSSETTLE register field macros
while at it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>