drm/sti: use u32 to store DMA addresses

The STi drm driver correctly warns about invalid format strings
when built with 64-bit dma_addr_t:

sti_hqvdp.c: In function 'sti_hqvdp_vtg_cb':
sti_hqvdp.c:605:119: warning: format '%x' expects argument of type
'unsigned int', but argument 5 has type 'dma_addr_t {aka long long
unsigned int}' [-Wformat=]
sti_hqvdp.c: In function 'sti_hqvdp_atomic_update':
sti_hqvdp.c:931:118: warning: format '%x' expects argument of type
'unsigned int', but argument 5 has type 'dma_addr_t {aka long long
unsigned int}' [-Wformat=]

This could be changed to using the %pad format string, but that
does not work when printing an rvalue, so instead I'm changing
the type in the sti_hqvdp structure to u32, which is what gets
written into the registers anyway.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Vincent Abriou <vincent.abriou@st.com>