mtd: nand: lpc32xx_mlc: Fix an error handling path in lpc32xx_nand_probe()

If 'clk_prepare_enable()' fails, we must 'put' the corresponding clock.

Fixes: 4d26f012 ("mtd: nand: lpc32xx_mlc: Handle return value of clk_prepare_enable.")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>