Add a comment about the MPSAFEness of this pccard_intr handler.  Given how we registered pccard_intr, it is MPSAFE.  However, since we register the pccard_intr handler with the flags of the ISR we call, that is the gating factor.  We need do nothing specific here.
Add a comment about the MPSAFEness of this pccard_intr handler.  Given
how we registered pccard_intr, it is MPSAFE.  However, since we
register the pccard_intr handler with the flags of the ISR we call,
that is the gating factor.  We need do nothing specific here.

Prompted by: seeing pccard_intr in a panic.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase