[media] sr030pc30: don't read a new pointer

sr030pc30_get_fmt() can only succeed if both info->curr_win and
info->curr_fmt are not NULL.

If one of those vars are null, the curent code would call:
	ret = sr030pc30_set_params(sd);

If the curr_win is null, it will return -EINVAL, as it would be
expected. However, if curr_fmt is NULL, the function won't
set it.

The code will then try to read from it:

        mf->code        = info->curr_fmt->code;
        mf->colorspace  = info->curr_fmt->colorspace;

with obviouly won't work.

This got reported by smatch:
	drivers/media/i2c/sr030pc30.c:505 sr030pc30_get_fmt() error: we previously assumed 'info->curr_win' could be null (see line 499)
	drivers/media/i2c/sr030pc30.c:507 sr030pc30_get_fmt() error: we previously assumed 'info->curr_fmt' could be null (see line 499)

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>