msm: ipa: Remove explicit usage of __iormb()

Explicit usage of the __iormb() is not advisable, as the
implementation of this function is architecture specific,
which will result in build failures if the signature of
__iormb() changes on a particular architecture.

Thus, replace explicit usages of readl_relaxed(), followed by
__iormb() with the readl() wrappers, as this achieves the
same effect, while abstracting the internal implementation
of __iormb().

Change-Id: Ic19aeb4955e5e8f1bc828e75902acf981a8ce68b
Signed-off-by: Ivaylo Georgiev <irgeorgiev@codeaurora.org>
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>