memshare: Perform Hypervisor mapping for boot-time allotted memory

The patch performs Hypervisor mapping for guaranteed memshare
client's allotted memory at boot time and prevent allocation for
clients with size zero and updates client's free memory count
variable after the successful allocation.
The patch also adds guard bytes to avoid NOC error while access
to memory allotted to diag because of resource group merging by TZ.

CRs-Fixed: 2026525, 2046258, 2062478
Change-Id: If9add2c593cd7bc88d68a8f2f2086d9c2aecf257
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>