msm: ipa3: Fix wrong references to SW shared memory size

IPA_SHARED_MEM_SIZE register contain the size of the SW partition in IPA
memory as well as its offset from the start.
At IPA driver we use wrong size of the region for size validity and
memory mapping with the partition size excluding the offset.

Change-Id: Ie06a786a449a6fdf4fc3df512d675967eb9b1775
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>
Signed-off-by: Amir Levy <alevy@codeaurora.org>