ARM: dts: msm: Do not halt before programming iommu registers for msm8994

Due to a hardware bug, SMMU hardware has to be halted before
programming a certain set of registers. This bug has been
fixed in msm8994. Removing the device tree tag which determines
if the hardware should halt or not.

Change-Id: Ieb063c21dba682e2d6eabe8a28dee9e4ff689be7
Signed-off-by: Neeti Desai <neetid@codeaurora.org>