spi: spi_bfin: update handling of delay-after-deselect

Move cs_chg_udelay handling (specific to this driver) to cs_deactive(), fixing
a bug when some SPI LCD driver needs delay after cs_deactive.

Fix bug reported by Cameron Barfield <cbarfield@cyberdata.net>
https://blackfin.uclinux.org/gf/project/uclinux-dist/forum/?action=ForumBrowse&forum_id=39&_forum_action=ForumMessageBrowse&thread_id=23630&feedback=Message%20replied.

Cc: Cameron Barfield <cbarfield@cyberdata.net>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>