but on "i2cexec". Create an i2cexec module (i2c_exec.c) to mirror the
dependencies in files.i2c and switch device drivers to depend on "i2cexec"
module instead.
A kernel with a USB stack and no I2C controller / bus attachment would spit
out a bunch of "WARNING: module error: can't find builtin dependency `iic'"
messages at boot. This change solves that problem.