Move the reading and parsing of a PF2VF message from the bottom half
function in adf_vf_isr.c, adf_pf2vf_bh_handler(), to the PFVF protocol
file adf_vf2pf_msg.c, for better code organization.

The receive and handle logic has been moved to a new function called
adf_recv_and_handle_pf2vf_msg() which returns a boolean indicating if
interrupts need to be re-enabled or not.
A slight refactoring has been done to avoid calculating the PF2VF CSR
offset twice and repeating the clearing of the PF2VFINT bit.

The "PF restarting" logic, now defined in the function
adf_pf2vf_handle_pf_restaring(), has been kept in adf_vf_isr.c due to
the dependencies with the adf_vf_stop_wq workqueue.
Signed-off-by: Marco Chiappero <marco.chiappero@intel.com>
Co-developed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>