[mlir][tosa] Rework tosa.apply_scale lowering for 32-bit

Added handling rounding behavior in 32-bits for when possible. This
avoids kernel compilation generating scalarized code on platforms where
64-bit vectors are not available.

As the 48-bit lowering requires 64-bit anyway, we added a full 64-bit
solution simplifying the old path.

Reviewed By: dcaballe, mravishankar

Differential Revision: https://reviews.llvm.org/D125583