dt-bindings: backlight: qcom-wled: Document ovp values for PMI8994

dt-bindings: backlight: qcom-wled: Document ovp values for PMI8994

Document ovp values supported by wled found in PMI8994.

Signed-off-by: Barnabás Czémán <barnabas.czeman@mainlining.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
Link: https://patch.msgid.link/20260116-pmi8950-wled-v3-1-e6c93de84079@mainlining.org
Signed-off-by: Lee Jones <lee@kernel.org>