OMAPDSS: Taal: fix compilation warning

This patch fixes a warning:

drivers/video/omap2/displays/panel-taal.c: In function
‘taal_num_errors_show’:
drivers/video/omap2/displays/panel-taal.c:529: warning: ‘errors’ may be
used uninitialized in this function

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>