hw/armv7m: Fix broken VMStateDescription

hw/armv7m: Fix broken VMStateDescription

In commit d5093d961585f02 we added a VMStateDescription to
the TYPE_ARMV7M object, to handle migration of its Clocks.
However a cut-and-paste error meant we used the wrong struct
name in the VMSTATE_CLOCK() macro arguments. The result was
that attempting a 'savevm' might result in an assertion
failure.

Cc: qemu-stable@nongnu.org
Buglink: https://gitlab.com/qemu-project/qemu/-/issues/803
Fixes: d5093d961585f02
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Ani Sinha <ani@anisinha.ca>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20220120151609.433555-1-peter.maydell@linaro.org