fbdev: uvesafb: Fixes an error handling path in uvesafb_probe()

If an error occurs after a successful uvesafb_init_mtrr() call, it must be
undone by a corresponding arch_phys_wc_del() call, as already done in the
remove function.

This has been added in the remove function in commit 63e28a7a
("uvesafb: Clean up MTRR code")

Fixes: 8bdb3a2d

 ("uvesafb: the driver core")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Helge Deller <deller@gmx.de>