diag: Sanitize the mempools with pool data size check

When allocating mempool memory sanitize the size check against
the pool data size. Update the pool data size as well whenever
itemsize is updated.

Change-Id: I7c426cfe35c35d5c2e7e5eefae710215097fbea0
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>