[roll] Roll fuchsia [vreg][fidl] Make Voltage interface in vreg FIDL return zx.status

Previously the fuchsia.hardware.vreg interface was only used to set the
voltage of a voltage regulator. As of fxrev.dev/1236544 the interface
can now also be used to enable/disable a regulator.

Some regulators may be fixed-voltage regulators that don't support
programming the voltage but may support the new Enable/Disable interface
only. Those regulators need a way to indicate that they do not support
the SetVoltageStep, GetVoltageStep, and GetRegulatorParams interfaces.

This CL allows those calls to also return a zx.Status so that they can
indicate that the method is not implemented.

Original-Bug: b/406156231
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1237804
Original-Revision: 8c04e0b3032aab13ca89cc55f1b047e078a0c494
GitOrigin-RevId: ec28a7bcad1f433dc3f722ad5859800c28fe79aa
Change-Id: I6016db608714fb56b6885fc525dce36be3a83a93
diff --git a/stem b/stem
index 1fecd5f..d963211 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
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              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="9f7d3d3f0147ad3ec823df901b8938631364b03f"/>
+             revision="8c04e0b3032aab13ca89cc55f1b047e078a0c494"/>
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