msm: ipa: prevent string buffer overflows in IPA driver

In IPA ioctls user-supplied data structures
contain string members,but there's no guarantee
they're null-terminated, add the string terminator
to prevent vulnerability of string buffer overflows

Change-Id: If79481d03201f405e5d95a525c8e69220d58a45f
Acked-by: Ashok Vuyyuru <avuyyuru@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>