.gitignore: ignore spl/ and tpl/ directories except spl/Makefile

Before this commit, output files under tpl/ directry
were not ignored.
This commit fixes this problem.

And we have only one source file under spl/ directory:
 spl/Makefile

So, we can describe .gitignore more simply.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

.gitignore

@@ -59,6 +59,10 @@
 /errlog
 /reloc_off
 
+/spl/
+!/spl/Makefile
+/tpl/
+
 /include/generated/
 /include/spl-autoconf.mk
 /include/tpl-autoconf.mk
@@ -88,6 +92,3 @@ GPATH
 GRTAGS
 GSYMS
 GTAGS
-
-# spl ais files
-/spl/*.ais

spl/.gitignore

-u-boot-spl
-u-boot-spl.bin
-u-boot-spl.lds
-u-boot-spl.map