hwmon: (pmbus/adm1266) Add Block process call

PmBus devices support Block Write-Block Read Process
Call described in SMBus specification v 2.0 with the
exception that Block writes and reads are permitted to
have up 255 data bytes instead of max 32 bytes (SMBus).

This patch adds Block WR process call support for ADM1266.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Link: https://lore.kernel.org/r/20200812142055.9213-3-alexandru.tachici@analog.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>