perf tests bp_account: Fix leaked file descriptor

Since the commit e9846f5ead26 ("perf test: In forked mode add check that
fds aren't leaked"), the test "Breakpoint accounting" reports the error:

# perf test -vvv "Breakpoint accounting"
20: Breakpoint accounting:
--- start ---
test child forked, pid 373
failed opening event 0
failed opening event 0
watchpoints count 4, breakpoints count 6, has_ioctl 1, share 0
wp 0 created
wp 1 created
wp 2 created
wp 3 created
wp 0 modified to bp
wp max created
---- end(0) ----
Leak of file descriptor 7 that opened: 'anon_inode:[perf_event]'

A watchpoint's file descriptor was not properly released. This patch
fixes the leak.

Fixes: 032db28e5fa3 ("perf tests: Add breakpoint accounting/modify test")
Reported-by: Aishwarya TCV <[e-mail]>
Signed-off-by: Leo Yan <[e-mail]>
Reviewed-by: Ian Rogers <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/tests/bp_account.c

···
 		fd_wp = wp_event((void *)&the_var, &attr_new);
 		TEST_ASSERT_VAL("failed to create max wp\n", fd_wp != -1);
 		pr_debug("wp max created\n");
+		close(fd_wp);
 	}
 
 	for (i = 0; i < wp_cnt; i++)