x86: Update mtrr functions to allow leaving cache alone

At present the mtrr functions disable the cache before making changes and
enable it again afterwards. This is fine in U-Boot, but does not work if
running in CAR (such as we are in SPL).

Update the functions so that the caller can request that caches be left
alone.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index 05cd7b7..2d897f8 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -77,8 +77,9 @@
  * possibly the cache.
  *
  * @state:	Empty structure to pass in to hold settings
+ * @do_caches:	true to disable caches before opening
  */
-void mtrr_open(struct mtrr_state *state);
+void mtrr_open(struct mtrr_state *state, bool do_caches);
 
 /**
  * mtrr_open() - Clean up after adjusting MTRRs, and enable them
@@ -86,8 +87,9 @@
  * This uses the structure containing information returned from mtrr_open().
  *
  * @state:	Structure from mtrr_open()
+ * @state:	true to restore cache state to that before mtrr_open()
  */
-void mtrr_close(struct mtrr_state *state);
+void mtrr_close(struct mtrr_state *state, bool do_caches);
 
 /**
  * mtrr_add_request() - Add a new MTRR request