With PC, there are 33 registers.  Three per line lines up nicely
without overflowing 80 columns.

Cc: qemu-stable@nongnu.org (3.0.1)
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>