video: fbdev: vesafb: add missed release_region

The driver forgets to free the I/O region in remove and probe
failure.
Add the missed calls to fix it.

Since the success of request_region() is optional, add the "region" field
in vesafb_par to represent whether request_region() succeeds.
Then only call release_region() when "region" is not null.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200329145839.20076-1-hslester96@gmail.com