acpi: Add an acpi command

It is useful to dump ACPI tables in U-Boot to see what has been generated.
Add a command to handle this.

To allow the command to find the tables, add a position into the global
data.

Support subcommands to list and dump the tables.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
diff --git a/cmd/Makefile b/cmd/Makefile
index 6692ed9..974ad48 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -11,6 +11,7 @@
 obj-y += version.o
 
 # command
+obj-$(CONFIG_CMD_ACPI) += acpi.o
 obj-$(CONFIG_CMD_AES) += aes.o
 obj-$(CONFIG_CMD_AB_SELECT) += ab_select.o
 obj-$(CONFIG_CMD_ADC) += adc.o