i2c: qcom-geni: release DMA channels on probe error

geni_i2c_init() grabs exclusive GPI tx/rx DMA channels when the serial
engine runs in GPI mode. If i2c_add_adapter() subsequently fails, probe
returns without releasing the channels, because the remove callback is
not invoked after a failed probe.

The adapter-registration failure path used to release the channels via
its err_dma label; that release was dropped when the probe tail was
restructured into geni_i2c_init().

Release the channels on the adapter-registration failure path, mirroring
geni_i2c_remove().

Fixes: d8d3bb127ad1 ("i2c: qcom-geni: Isolate serial engine setup")
Assisted-by: GLM:5.3
Signed-off-by: Shengzhuo Wei <me@cherr.cc>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Mukesh Kumar Savaliya <mukesh.savaliya@oss.qualcomm.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://patch.msgid.link/20260827-i2c-dma-channel-leak-v1-3-271d4adc03a0@cherr.cc