arm64/ptrace: Support access to TPIDR2_EL0

arm64/ptrace: Support access to TPIDR2_EL0

SME introduces an additional EL0 register, TPIDR2_EL0, intended for use
by userspace as part of the SME. Provide ptrace access to it through the
existing NT_ARM_TLS regset used for TPIDR_EL0 by expanding it to two
registers with TPIDR2_EL0 being the second one.

Existing programs that query the size of the register set will be able
to observe the increased size of the register set. Programs that assume
the register set is single register will see no change. On systems that
do not support SME TPIDR2_EL0 will read as 0 and writes will be ignored,
support for SME should be queried via hwcaps as normal.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829154921.837871-4-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>