lm32: take BQL before writing IP/IM register
    
    Writing to these registers may raise an interrupt request. Actually,
    this prevents the milkymist board from starting.
    
    Cc: qemu-stable@nongnu.org
    Signed-off-by: Michael Walle <michael@walle.cc>
    Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
    Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
    (cherry picked from commit 81e9cbd0ca1131012b058df6804b1f626a6b730c)
    Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>