grep: remove redundant "fixed" field re-assignment to 0

Remove the redundant re-assignment of the fixed field to zero right
after the entire struct has been set to zero via memset(...).

Unlike some nearby commits this pattern doesn't date back to the
pattern described in e0b9f8a ("grep: remove redundant regflags
assignments", 2017-05-25), instead it was apparently cargo-culted in
9ecedde ("Use kwset in grep", 2011-08-21).

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

grep.c

@@ -626,8 +626,6 @@ static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
 	    has_null(p->pattern, p->patternlen) ||
 	    is_fixed(p->pattern, p->patternlen))
 		p->fixed = !icase || ascii_only;
-	else
-		p->fixed = 0;
 
 	if (p->fixed) {
 		p->kws = kwsalloc(icase ? tolower_trans_tbl : NULL);