Mali: prevent build with 64-bit DMA addresses

Mali uses pointers to store DMA addresses (mali_io_address), which are
naturally 32-bit on this platform.

So when the kernel is built with 64-bit dma_addr_t, Mali fails in a
cryptic way.

mali_allocate_empty_page() calls mali_mmu_get_table_page(),
which leads to mali_mem_os_get_table_page(), where we pass a
32-bit mali_io_address as the phys (dma_addr_t) parameter to
dma_alloc_writecombine.

Shortly after, when the DMA layer comes to write a 64-bit value into
this variable, it ends up spilling over the allocated 32-bits and causing
stack corruption.

In this case, the stack corruption hits mali_mmu_initialize(), causing it
to lose the address where it was going to store the result from
mali_empty_page_directory_phys(). It tries to write it into address 0,
and the resultant boot-time crash looks like:

 Unable to handle kernel NULL pointer dereference at virtual address 00000000
 PC is at mali_mmu_initialize+0x24/0x118
 LR is at mali_allocate_empty_page+0x114/0x128
 pc : [<c03c42d4>]    lr : [<c03c53b8>]    psr: 20000113
 sp : c7079dd8  ip : 00000000  fp : c0953330
 r10: c7491200  r9 : 00000000  r8 : c7228210
 r7 : c0a1079c  r6 : 00000000  r5 : c0aa5e04  r4 : 00000000
 r3 : 00000a6b  r2 : c9843000  r1 : 60000193  r0 : 49843000
 Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
 Control: 10c5387d  Table: 4000404a  DAC: 00000015
 [<c03c42d4>] (mali_mmu_initialize) from [<c03beef4>] (mali_initialize_subsystems+0x2fc/0x810)
 [<c03beef4>] (mali_initialize_subsystems) from [<c03c09c8>] (mali_probe+0x84/0x708)
 [<c03c09c8>] (mali_probe) from [<c03f252c>] (platform_drv_probe+0x2c/0x5c)

Add a compile check here to avoid wasting time on this again...