x86: baytrail: Add .gitignore for ACPI enabled boards

Let git ignore dsdt.aml, dsdt.asl.tmp and dsdt.c files.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

board/congatec/conga-qeval20-qa3-e3845/.gitignore

@@ -0,0 +1,3 @@
+dsdt.aml
+dsdt.asl.tmp
+dsdt.c

board/intel/bayleybay/.gitignore

@@ -0,0 +1,3 @@
+dsdt.aml
+dsdt.asl.tmp
+dsdt.c

board/intel/minnowmax/.gitignore

@@ -0,0 +1,3 @@
+dsdt.aml
+dsdt.asl.tmp
+dsdt.c