drm/amd/display: fix incorrrect valid irq check

valid DAL irq should be < DAL_IRQ_SOURCES_NUMBER.

Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-and-tested-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org