target/hexagon: remove unused variable

target/hexagon: remove unused variable

When building with clang version 13.0.0 (eg. Fedora 13.0.0-3.fc35),
two unused variables introduced by macro GATHER_FUNCTION and
SCATTER_FUNCTION will cause building process failure due to
[-Werror -Wunused-variable].

Signed-off-by: Zongyuan Li <zongyuan.li@smartx.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/831
Message-Id: <20220124064339.56027-1-zongyuan.li@smartx.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>