x86: sandbox: Add a PMC emulator and test

Add a simple PMC for sandbox to permit tests to run.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/power/acpi_pmc/Kconfig b/drivers/power/acpi_pmc/Kconfig
index 472a61a..fcd50e3 100644
--- a/drivers/power/acpi_pmc/Kconfig
+++ b/drivers/power/acpi_pmc/Kconfig
@@ -23,3 +23,12 @@
 	  provides features including checking whether the system started from
 	  resume, powering off the system and enabling/disabling the reset
 	  mechanism.
+
+config ACPI_PMC_SANDBOX
+	bool "Test power manager (PMC) for sandbox"
+	depends on ACPI_PMC && SANDBOX
+	help
+	  This driver emulates a PMC (Power-Management Controller) so that
+	  the uclass logic can be tested. You can use the 'pmc' command to
+	  access information from the driver. It uses I/O access to read
+	  from the PMC.