div64.h:do_div() bug

[Artur Klauser]

I've found that a bug in asm-arm/div64.h:do_div() is preventing correct
conversion of timestamps in smbfs (and probably ntfs as well) from NT to
Unix format. I'll post a patch that fixes the bug, but I think it is also
present in other architectures - at least SPARC, SH, and CRIS look
suspicious.

If people with access to these architectures could run the following small 
test and let me know the outcome, I can fix it there too - thanks.

//-----------------------------------------------------------------------------
#define __KERNEL__
#include <asm/types.h> // get kernel definition of u64, u32
#undef __KERNEL__
#include <asm/div64.h> // get definition of do_div()
#include <stdio.h>

main () {
  union {
    u64 n64;
    u32 n32[2];
  } in, out;

  in.n32[0] = 1;
  in.n32[1] = 1;
  out = in;

  do_div(out.n64, 1);

  if (in.n64 != out.n64) {
    printf("FAILURE: asm/div64.h:do_div() is broken for 64-bit dividends\n");
    exit(1);
  } else {
    printf("Congratulations: asm/div64.h:do_div() handles 64-bit dividends\n");
  }
  return 0;
}
//-----------------------------------------------------------------------------
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