fallocate06: Increase test loop device size to 1GB

Btrfs on newer kernels may have issues with running out of space
for metadata in the fill FS+CoW subtest if the test device is too
small. Increase minimal device size to avoid the corner case.

Signed-off-by: Martin Doucha <mdoucha@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>

testcases/kernel/syscalls/fallocate/fallocate06.c

@@ -260,6 +260,8 @@ static struct tst_test test = {
 	.test = run,
 	.tcnt = ARRAY_SIZE(testcase_list),
 	.needs_root = 1,
+	.dev_min_size = 1024,
+	.max_runtime = 120,
 	.mount_device = 1,
 	.mntpoint = MNTPOINT,
 	.all_filesystems = 1,