dt-bindings: power: Rename back power_domain.txt bindings to fix references

With split of power domain controller bindings to power-domain.yaml,
the consumer part was renamed to power-domain.txt breaking the
references.  Undo the renaming.
Reported-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Fixes: 5279a3d8 ("dt-bindings: power: Convert Generic Power Domain bindings to json-schema")
Signed-off-by: NKrzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: NRob Herring <robh@kernel.org>

MAINTAINERS

@@ -6882,7 +6882,7 @@ L:	linux-pm@vger.kernel.org
 S:	Supported
 F:	drivers/base/power/domain*.c
 F:	include/linux/pm_domain.h
-F:	Documentation/devicetree/bindings/power/power-domain*
+F:	Documentation/devicetree/bindings/power/power?domain*
 
 GENERIC RESISTIVE TOUCHSCREEN ADC DRIVER
 M:	Eugen Hristev <eugen.hristev@microchip.com>