qat: refactor error handling and add mutex locks

Error handling in qat driver code has been refactored.
Mutex lock handling has also been added during driver
attach and detach. Also pci_disable_busmaster() is called in
adf_detach() to ensure proper cleanup during device detachment.

Reviewed by: markj, ziaee
MFC after: 2 weeks
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D50379