efi: Support showing tables

Add a command (for the app and payload) to display the tables provided
by EFI. Note that for the payload the tables should always be present, so
an error message is unnecessary and would bloat the code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/cmd/efi.rst b/doc/usage/cmd/efi.rst
index c029c42..ef37ff2 100644
--- a/doc/usage/cmd/efi.rst
+++ b/doc/usage/cmd/efi.rst
@@ -10,6 +10,7 @@
 ::
 
     efi mem [all]
+    efi tables
 
 Description
 -----------
@@ -54,6 +55,14 @@
     Shows a code for memory attributes. The key for this is shown below the
     table.
 
+efi tables
+~~~~~~~~~~
+
+This shows a list of the EFI tables provided in the system table. These use
+GUIDs so it is not possible in general to show the name of a table. But some
+effort is made to provide a useful table, where the GUID is known by U-Boot.
+
+
 Example
 -------
 
@@ -195,3 +204,16 @@
      f: uncached, write-coalescing, write-through, write-back
     rf: uncached, write-coalescing, write-through, write-back, needs runtime mapping
      1: uncached
+
+
+    => efi tables
+    000000001f8edf98  ee4e5898-3914-4259-9d6e-dc7bd79403cf  EFI_LZMA_COMPRESSED
+    000000001ff2ace0  05ad34ba-6f02-4214-952e-4da0398e2bb9  EFI_DXE_SERVICES
+    000000001f8ea018  7739f24c-93d7-11d4-9a3a-0090273fc14d  EFI_HOB_LIST
+    000000001ff2bac0  4c19049f-4137-4dd3-9c10-8b97a83ffdfa  EFI_MEMORY_TYPE
+    000000001ff2cb10  49152e77-1ada-4764-b7a2-7afefed95e8b  (unknown)
+    000000001f9ac018  060cc026-4c0d-4dda-8f41-595fef00a502  EFI_MEM_STATUS_CODE_REC
+    000000001f9ab000  eb9d2d31-2d88-11d3-9a16-0090273fc14d  SMBIOS table
+    000000001fb7e000  eb9d2d30-2d88-11d3-9a16-0090273fc14d  EFI_GUID_EFI_ACPI1
+    000000001fb7e014  8868e871-e4f1-11d3-bc22-0080c73c8881  ACPI table
+    000000001e654018  dcfa911d-26eb-469f-a220-38b7dc461220  (unknown)