drm/amdgpu/display: remove redundant continue statement

The continue statement in a for-loop is redudant and can be removed.
Clean up the code to address this.

Addresses-Coverity: ("Continue as no effect")
Fixes: b6f91fc1

 ("drm/amdgpu/display: buffer INTERRUPT_LOW_IRQ_CONTEXT interrupt work")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>