MIPS: Alchemy: Fix an out-of-bound access in db1200_dev_setup()

[ Upstream commit 89c4b588d11e9acf01d604de4b0c715884f59213 ]

When calling spi_register_board_info(), we should pass the number of
elements in 'db1200_spi_devs', not 'db1200_i2c_devs'.

Fixes: 63323ec5 ("MIPS: Alchemy: Extended DB1200 board support.")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>