fs/ext2: replace ternary operator with min_t()

fs/ext2: replace ternary operator with min_t()

Fix the following coccicheck warning:

fs/ext2/super.c:1494: WARNING opportunity for min().
fs/ext2/super.c:1533: WARNING opportunity for min().

min_t() macro is defined in include/linux/minmax.h. It avoids
multiple evaluations of the arguments when non-constant and performs
strict type-checking.

Link: https://lore.kernel.org/r/20220714063318.1777139-1-13667453960@163.com
Signed-off-by: Jiangshan Yi <yijiangshan@kylinos.cn>
Signed-off-by: Jan Kara <jack@suse.cz>