test: Add test for new command pci_mps

Adds a test for the new pci_mps command to ensure that it can set the
Maximum Payload Size (MPS) of all devices to 256 bytes in the sandbox
environment. Enables the pci_mps command in the sandbox environment so
that this test can be run.

Signed-off-by: Stephen Carlson <stcarlso@linux.microsoft.com>
diff --git a/include/test/suites.h b/include/test/suites.h
index 7c4960c..7349ce5 100644
--- a/include/test/suites.h
+++ b/include/test/suites.h
@@ -48,6 +48,8 @@
 int do_ut_optee(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]);
 int do_ut_overlay(struct cmd_tbl *cmdtp, int flag, int argc,
 		  char *const argv[]);
+int do_ut_pci_mps(struct cmd_tbl *cmdtp, int flag, int argc,
+		  char *const argv[]);
 int do_ut_print(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]);
 int do_ut_seama(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]);
 int do_ut_setexpr(struct cmd_tbl *cmdtp, int flag, int argc,