cpu-all.h: Don't accidentally sign extend in g2h()

cpu-all.h: Don't accidentally sign extend in g2h()

Cast the argument of the g2h() macro to a target_ulong so that
it isn't accidentally sign-extended if it is a signed 32 bit
type and long is a 64 bit type. In particular, this fixes a
bug where it would return the wrong value for 32 bit guests
on 64 bit hosts when passed in one of the arg* values from
do_syscall() [which are all abi_long and thus signed types].
This could result in spurious failure of mlock(), among others.

Reviewed-by: Andreas F=E4rber <afaerber@suse.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>