mhu_v3: removes check of 4 bytes buffer size alignment

For mhu_v3 transfer there is no hard requirement of 4 Byte alignment of
buffer size. This patch removes the 4 Bytes conditional check for buffer
size alignment.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Signed-off-by: Sathyam Panda <sathyam.panda@arm.com>
Change-Id: Ie8c53bee6a304da8429a6c3060ab80dabf2483a0