msm: mhi_dev: Fix interrupt storm during Enable/disable

mhi_dev_backup_mmio() and mhi_dev_restore_mmio() does backup/restore
of INTR registers of MHI device, causing it to restore interrupts
that are not valid during PCIE PM_RST_DEAST event. The fix is to
skip the INTR register space.

Change-Id: I2a8cde174cf4c6acd7acce13ad0195ed6a9a6f0b
Signed-off-by: Subramanian Ananthanarayanan <skananth@codeaurora.org>
Signed-off-by: Gauri Joshi <gaurjosh@codeaurora.org>