SAMA5D HSMCI: Fix a problem on card insertion/removal callback handling. ...

SAMA5D HSMCI: Fix a problem on card insertion/removal callback handling.  Interrupts were being disable so that the callbacks occurred with interrupts disabled.  This resulted in loss of some interrupts and some not-so-good behaviors.  The solution is to perform all callbacks on the work thread unconditionally (2014-7-29).