[IR] Remove unbounded as possible value for vscale_range minimum

The default for min is changed to 1. The behaviour of -mvscale-{min,max}
in Clang is also changed such that 16 is the max vscale when targeting
SVE and no max is specified.

Reviewed By: sdesmalen, paulwalker-arm

Differential Revision: https://reviews.llvm.org/D113294

GitOrigin-RevId: 698584f89b8f8bd7f6c2d2cd61efb5548857da2a
6 files changed