media: ti-vpe: cal: Rename cal_create_instance() to cal_ctx_create()

The cal_create_instance() function creates a CAL context. Rename it to
cal_ctx_create() to make its purpose more explicit.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>