acpi_iicbus: Shift slave address
The address is expected to need shifting.
see https://uefi.org/specs/ACPI/6.5/13_System_Mgmt_Bus_Interface_Specification.html#smbus-slave-addresses
Reviewed by: imp, markj, Elliott Mitchell
Pull Request: https://github.com/freebsd/freebsd-src/pull/1125
(cherry picked from commit 67677a654aa7456f18077ccbaa9c40f39a36d21a)