tegra210-adma: fix 32-bit x86 build

The Tegra210 Audio DMA controller driver did a plain divide:

	page_no = (res_page->start - res_base->start) / cdata->ch_base_offset;

which causes problems on 32-bit x86 configurations that have 64-bit
resource sizes:

  x86_64-linux-ld: drivers/dma/tegra210-adma.o: in function `tegra_adma_probe':
  tegra210-adma.c:(.text+0x1322): undefined reference to `__udivdi3'

because gcc doesn't generate the trivial code for a 64-by-32 divide,
turning it into a function call to do a full 64-by-64 divide.  And the
kernel intentionally doesn't provide that helper function, because 99%
of the time all you want is the narrower version.

Of course, tegra210 is a 64-bit architecture and the 32-bit x86 build is
purely for build testing, so this really is just about build coverage
failure.

But build coverage is good.

Side note: div_u64() would be suboptimal if you actually have a 32-bit
resource_t, so our "helper" for divides are admittedly making it harder
than it should be to generate good code for all the possible cases.

At some point, I'll consider 32-bit x86 so entirely legacy that I can't
find it in myself to care any more, and we'll just add the __udivdi3
library function.

But for now, the right thing to do is to use "div_u64()" to show that
you know that you are doing the simpler divide with a 32-bit number.
And the build error enforces that.

While fixing the build issue, also check for division-by-zero, and for
overflow.  Which hopefully cannot happen on real production hardware,
but the value of 'ch_base_offset' can definitely be zero in other
places.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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