acpi: Add myself as maintainer

Add myself as maintainer of the generic ACPI code, until someone else
steps up to take it on.

Signed-off-by: Simon Glass <sjg@chromium.org>

MAINTAINERS

@@ -50,6 +50,12 @@ so much easier [Ed]
 Maintainers List (try to look for most precise areas first)
 
 		-----------------------------------
+ACPI:
+M:	Simon Glass <sjg@chromium.org>
+S:	Maintained
+F:	cmd/acpi.c
+F:	lib/acpi/
+
 ANDROID AB
 M:	Igor Opaniuk <igor.opaniuk@gmail.com>
 R:	Sam Protsenko <joe.skb7@gmail.com>