dt-bindings: mfd: sprd,sc2731: Reference sprd,sc2731-efuse bindings

Directly reference the sc2731-efuse bindings to simplify the schema.
Remove the duplicate example from the efuse bindings.
While at it, add the "pmic_adc" label that was missed during the
initial YAML conversion.

Signed-off-by: Stanislav Jakubek <stano.jakubek@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/Z1_9ROiI2ZHKsbAD@standask-GA-A55M-S2HP


Signed-off-by: Lee Jones <lee@kernel.org>