diag: Sanitize the mempools with pool data size check

BugLink: https://bugs.launchpad.net/bugs/1931727



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>
Signed-off-by: Vivek Golani <vgolani@codeaurora.org>
(cherry picked from commit 8aa81ef041a6d3e43f44872ced985c7ea10796f7)
Signed-off-by: Shrirang Bagul <shrirang.bagul@canonical.com>