R600: Don't set BypassSlowDiv for 64-bit division

R600: Don't set BypassSlowDiv for 64-bit division

BypassSlowDiv is used by codegen prepare to insert a run-time
check to see if the operands to a 64-bit division are really 32-bit
values and if they are it will do 32-bit division instead.

This is not useful for R600, which has predicated control flow since
both the 32-bit and 64-bit paths will be executed in most cases.  It
also increases code size which can lead to more instruction cache
misses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218252 91177308-0d34-0410-b5e6-96231b3b80d8