arch-arm: Fix XN in TLB permissions
arch-arm: Fix XN in TLB permissions

The SIF condition check should be logically ORed with the TLB
entry XN attribute, instead of overriding it.

Change-Id: I70b38d97bbdc82b9f385d40ad06546785fc2c5bb
Signed-off-by: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Reviewed-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32635
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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