hw/pxa2xx_dma.c: drop target_phys_addr_t usage in device state

Pxa2xx DMA controller is a 32-bit device and it has no knowledge of system's
physical address size, so it should not use target_phys_addr_t in it's state.
Convert variables descr, src and dest from type target_phys_addr_t to uint32_t,
use VMSTATE_UINT32 instead of VMSTATE_UINTTL for these variables.

We can do this safely because:
1) pxa2xx actually has 32-bit physical address size;
2) rest of the code in file never assumes descr, src and dest variables to have
size different from uint32_t;
3) we shouldn't have used VMSTATE_UINTTL in the first place because this macro
is for target_ulong type (which can be different from target_phys_addr_t).

Signed-off-by: Igor Mitsyanko <i.mitsyanko@samsung.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>