Secure DPU: Allocate buffer from NS

New commands are added to the secure DPU:

SECURE_DPU_CMD_ALLOCATE_BUFFER: this command sends the request to NS
for allocating buffer with buffer length as the argument. The response
indicates the handle used to map the buffer on the Trusty.

Bug: 176508588
Change-Id: Ida8cbee736bb77928b4abfe45fad059930ae2bc9
3 files changed