x86: Avoid using hardcoded number of variable range MTRRs in mtrr_commit()

Since commit 29d2d64e ("x86: Add support for more than 8 MTRRs"),
the maximum number of variable range MTRRs was increased from 8 to 10.
On the BayTrail platform there are only 8 variable range MTRRs. In
mtrr_commit() it still uses MTRR_MAX_COUNT which caused a #GP during
VESA video driver probe. It should have been updated to use dynamically
probed number.

This fixes the boot failure seen on Intel Minnow Max board.

Fixes: 29d2d64e

 ("x86: Add support for more than 8 MTRRs")
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/mtrr.c

@@ -158,7 +158,7 @@ int mtrr_commit(bool do_caches)
 
 	/* Clear the ones that are unused */
 	debug("clear\n");
-	for (; i < MTRR_MAX_COUNT; i++)
+	for (; i < mtrr_get_var_count(); i++)
 		wrmsrl(MTRR_PHYS_MASK_MSR(i), 0);
 	debug("close\n");
 	mtrr_close(&state, do_caches);