refactor: remove out parameter from `allocate_share_state`

`allocate_share_state` returned a `struct ffa_memory_share_state *` via
an out parameter and indicated success by returning a `bool`. This patch
removes the out parameter and returns the `struct ffa_memory_share_state
*` directly.

Change-Id: I3d0bd0952d39332282b9303c0cb60850317cd8e3
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
3 files changed