Staging: fbtft: Fix some typo. pdc8544 --> pcd8544

The driver is related to 'pcd8544'.
However, 2 strings are about pdc8544 (c and d switched)
Fix it.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20190725183856.17616-1-christophe.jaillet@wanadoo.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>