checkpatch: Fix regular expressions

When generating the list of files to check by checkpatch.pl, the list
generated by `git ls-files` is filtered by a regular expression with
grep. Due to a malformed regex, the dot of `.md` was considered a
wildcard instead of a dot. This patch fixes this so that it matches
only dots, thus allowing the two following files to be checked:

* tools/cert_create/include/cmd_opt.h
* tools/cert_create/src/cmd_opt.c

Also extended the list of library directories to check by checkpatch
to exclude any folder starting with libfdt.

Change-Id: Ie7bf18efe4df29e364e5d67ba1118515304ed9a4
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Makefile

@@ -66,7 +66,7 @@ INC_DIRS_TO_CHECK	:=	$(sort $(filter-out			\
 					include/lib,			\
 					$(wildcard include/*)))
 LIB_DIRS_TO_CHECK	:=	$(sort $(filter-out			\
-					lib/libfdt			\
+					lib/libfdt%			\
 					lib/stdlib,			\
 					$(wildcard lib/*)))
 ROOT_DIRS_TO_CHECK	:=	$(sort $(filter-out			\
@@ -568,7 +568,7 @@ realclean distclean:
 checkcodebase:		locate-checkpatch
 	@echo "  CHECKING STYLE"
 	@if test -d .git ; then						\
-		git ls-files | grep -E -v libfdt\|stdlib\|docs\|\.md |	\
+		git ls-files | grep -E -v 'libfdt|stdlib|docs|\.md' |	\
 		while read GIT_FILE ;					\
 		do ${CHECKPATCH} ${CHECKCODE_ARGS} -f $$GIT_FILE ;	\
 		done ;							\