fix(pie): invalidate data cache in the entire image range if PIE is enabled

Currently on image entry, the data cache in the RW address range is
invalidated before MMU is enabled to safeguard against potential
stale data from previous firmware stage. If PIE is enabled however,
RO sections including the GOT may be also modified during pie fixup.
Therefore, to be on the safe side, invalidate the entire image
region if PIE is enabled.

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Change-Id: I7ee2a324fe4377b026e32f9ab842617ad4e09d89
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/225704


Reviewed-by: CITOOLS <MDG-smet-aci-reviews@list.st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@foss.st.com>
Reviewed-by: Sebastien PASDELOUP <sebastien.pasdeloup-ext@st.com>
Tested-by: Yann GAUTIER <yann.gautier@foss.st.com>