target/hexagon: rename aliased register HEX_REG_P3_0

target/hexagon: rename aliased register HEX_REG_P3_0

The patch renames the identifier of the 32bit register
HEX_REG_P3_0 to HEX_REG_P3_0_ALIASED.

This change is to intended to provide some warning that
HEX_REG_P3_0 is an aliased register which has multiple
representations in CPU state and therefore might require
special handling in some contexts. The hope is to prevent
accidental misuse of this register e.g the issue reported
for the signals tests failure [here][1].

[1]: https://lists.gnu.org/archive/html/qemu-devel/2021-11/msg01102.html

Signed-off-by: Mukilan Thiyagarajan <quic_mthiyaga@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <20221229092006.10709-3-quic_mthiyaga@quicinc.com>