kselftest/arm64: Fix redundancy of a testcase

kselftest/arm64: Fix redundancy of a testcase

Currently, we are writing the same value as we read into the TLS
register, hence we cannot confirm update of the register, making the
testcase "verify_tpidr_one" redundant. Fix this.

Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240605115448.640717-1-dev.jain@arm.com
[catalin.marinas@arm.com: remove the increment style change]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>