arch-arm: Remove SPSR write mask
arch-arm: Remove SPSR write mask

We are currently masking out the PAN and UAO field when writing
to the SPSR_ELx register.
This is not needed and we should treat them as RES0 instead if
FEAT_PAN and FEAT_UAO are not implemented

Change-Id: Ib65e3744f365825d2414b8092b3a79324be461b4
Signed-off-by: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/50389
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Maintainer: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>

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