jammy-amd64-tf-a-build: Use explicit Rust version; update to 1.88.0

Last commit (3b16008ad2fe380133ee2d4a10fb0018fed952ca) fixed the
version to 1.85.0. See commit for more information.

Add support for a later toolchain, namely, 1.88.0

Change-Id: I0d269c619fbf6756c4c3101a102481a13a678056
Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
1 file changed