MFSH_UNPHYSTOVIRT - Mark completion of use of virtual address

Release the selector allocated previously by calling MFSH_PHYSTOVIRT. 
Calling Sequence   

int far pascal MFSH_UNPHYSTOVIRT(usSel)

unsigned short usSel;

usSel contains the selector to released. 
If no error is detected, a zero error code is returned. If an error is 
detected, the following error code is returned: 
the supplied selector is invalid. 
This helper is for use by a mini-FSD with an imbedded device driver. It is 
the same as the standard device driver UNPHYSTOVIRT helper. 
A caller must issue a corresponding UNPHYSTOVIRT after calling PHYSTOVIRT, 
before returning to its caller or using any other helpers. 

Created using Inf-PHP v.2 (c) 2003 Yuri Prokushev
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