x86: Add msr command

It is useful to obtain the results of MSR queries as well as to update
MSR registers, so add a command these tasks.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/cmd/Makefile b/test/cmd/Makefile
index 302c748..4080835 100644
--- a/test/cmd/Makefile
+++ b/test/cmd/Makefile
@@ -12,7 +12,7 @@
 obj-$(CONFIG_CMD_PAUSE) += test_pause.o
 endif
 obj-y += exit.o mem.o
-obj-$(CONFIG_X86) += cpuid.o
+obj-$(CONFIG_X86) += cpuid.o msr.o
 obj-$(CONFIG_CMD_ADDRMAP) += addrmap.o
 obj-$(CONFIG_CMD_BDI) += bdinfo.o
 obj-$(CONFIG_CMD_FDT) += fdt.o