Trivial fix to .gitignore for spl/Makefile

Trivial fix to .gitignore for spl/Makefile

According to the gitignore man page:

"An optional prefix "!" which negates the pattern; any matching file
excluded by a previous pattern will become included again."
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
So the directory exclude "/spl/*" must come before the exception
for spl/Makefile otherwise it has no effect.
Signed-off-by: NRalph Siemsen <ralphs@netwinder.org>
Tested-by: Masahiro Yamada <yamada.m@jp.panasonic.com> [on git v1.7.9.5 / v1.8.3.2]

.gitignore

@@ -47,8 +47,8 @@
 /errlog
 /reloc_off
 
-!/spl/Makefile
 /spl/*
+!/spl/Makefile
 /tpl/
 
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