This function Frees a memory block previously allocated with the Allocate
Memory Block function (0501h).
In:
AX = 0502h
SI:DI = memory block handle
Out:
if successful:
carry flag clear
if failed:
carry flag set
Notes:
No descriptors are freed by this call. It is the client's responsibility to
free any descriptors that it previously allocated to map the memory block.
Descriptors should be freed before memory blocks.