scripts/tags.sh: Fix warnings "null expansion of name pattern"

Warnings such as
ctags: Warning: include/linux/wait_bit.h:59: null expansion of name pattern "\1"
are triggered when parsing DECLARE_BITMAP() inside comments,
resulting in an empty token.

To avoid this, ensure only non-empty tokens.

Signed-off-by: Costa Shulyupin <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: makelinux

scripts/tags.sh

@@ -191,7 +191,7 @@ regex_c=(
 	'/\<DEFINE_\(RT_MUTEX\|MUTEX\|SEMAPHORE\|SPINLOCK\)([[:space:]]*\([[:alnum:]_]*\)/\2/v/'
 	'/\<DEFINE_\(RAW_SPINLOCK\|RWLOCK\|SEQLOCK\)([[:space:]]*\([[:alnum:]_]*\)/\2/v/'
 	'/\<DECLARE_\(RWSEM\|COMPLETION\)([[:space:]]*\([[:alnum:]_]\+\)/\2/v/'
-	'/\<DECLARE_BITMAP([[:space:]]*\([[:alnum:]_]*\)/\1/v/'
+	'/\<DECLARE_BITMAP([[:space:]]*\([[:alnum:]_]\+\)/\1/v/'
 	'/\(^\|\s\)\(\|L\|H\)LIST_HEAD([[:space:]]*\([[:alnum:]_]*\)/\3/v/'
 	'/\(^\|\s\)RADIX_TREE([[:space:]]*\([[:alnum:]_]*\)/\2/v/'
 	'/\<DEFINE_PER_CPU([^,]*,[[:space:]]*\([[:alnum:]_]*\)/\1/v/'