Split crypto_driver.h into 4:
* crypto_driver_common.h for common definitions, not meant to be
included directly by driver code.
* crypto_accel_driver.h for drivers that work with transparent
key material.
* crypto_se_driver.h for drivers that work with opaque key
material.
* crypto_entropy_driver.h for drivers of entropy sources.
There is no code change in this commit, I only moved some code around.
