ti: common: board_detect: Set alen to expected value before i2c read

In non DM I2C read operations the address length passed in during a read
operation will be used automatically. However, in DM I2C the address length
is set to a default value of one which causes problems when trying to
perform a read with a differing alen. Therefore, before the first read in a
series of read operations set the alen to the correct value.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Heiko Schocher <hs@denx.de>