msm: ep_pcie: Update MSI configuration

Update check for valid MSI enable and setting using
MSI_ENABLE bit instead of address and data. Host can
set address and data to 0 therefore check if MSI_ENABLE
is set.

Change-Id: I686c3ed155b8c5c843d12a49218f4720655dcc18
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>