dt-bindings: mfd: x-powers,axp152: add boost regulator

dt-bindings: mfd: x-powers,axp152: add boost regulator

The X-Powers AXP717 contains a boost regulator, that it meant to provide
the 5V USB VBUS voltage when the devices operates on battery.

Add the name "boost" to the regexp describing the allowed node names,
to allow the regulator to be described in the devicetree.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Lee Jones <lee@kernel.org>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Link: https://patch.msgid.link/20240816001824.6028-2-andre.przywara@arm.com
Signed-off-by: Mark Brown <broonie@kernel.org>