drm/exynos: Delete an error message in three functions

The function “platform_get_irq” can log an error already.
Thus omit redundant messages for the exception handling in the
calling functions.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Inki Dae <inki.dae@samsung.com>