target/hexagon: Drop include of qemu.h

target/hexagon: Drop include of qemu.h

The qemu.h file is a CONFIG_USER_ONLY header; it doesn't appear on
the include path for softmmu builds.  Currently we include it
unconditionally in target/hexagon/op_helper.c.  We used to need it
for the put_user_*() and get_user_*() functions, but now that we have
removed the uses of those from op_helper.c, the only reason it's
still there is that we're implicitly relying on it pulling in some
other headers.

Explicitly include the headers we need for other functions, and drop
the include of qemu.h.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20210717103017.20491-1-peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>