Cactus: cmd for mem share tests

Previously there was no cmd id for the mem share tests in
'cactus_test_cmds.h', the func id was being reused. For consistency
added the cmd id 'CACTUS_MEM_SEND_CMD'.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: Ia2cee00d444d2b753855f2323578df0f9bcf4fb2
3 files changed