drm/bridge: synopsys: dw-dp: fix error paths of dw_dp_bind

drm/bridge: synopsys: dw-dp: fix error paths of dw_dp_bind

Fix several issues in dw_dp_bind() error handling:

1. Missing return after drm_bridge_attach() failure - the function
   continued execution instead of returning an error.

2. Resource leak: drm_dp_aux_register() is not a devm function, so
   drm_dp_aux_unregister() must be called on all error paths after
   aux registration succeeds. This affects errors from:
   - drm_bridge_attach()
   - phy_init()
   - devm_add_action_or_reset()
   - platform_get_irq()
   - devm_request_threaded_irq()

3. Bug fix: platform_get_irq() returns the IRQ number or a negative
   error code, but the error path was returning ERR_PTR(ret) instead
   of ERR_PTR(dp->irq).

Use a goto label for cleanup to ensure consistent error handling.

Fixes: 86eecc3a9c2e ("drm/bridge: synopsys: Add DW DPTX Controller support library")
Cc: stable@vger.kernel.org
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://patch.msgid.link/20260102155553.13243-1-osama.abdelkader@gmail.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>