shader_recompiler: Implement ISBERD instruction

Implements the Internal Stage Buffer Entry Read (ISBERD) instruction in the
Maxwell shader recompiler. This replaces the previous stubbed implementation
with actual buffer reading functionality.

The implementation:
- Validates unsupported features (skew, o, mode, shift)
- Performs buffer read using IR::InternalStageBufferRead
- Stores the read value to the destination register

This removes the "(STUBBED) called" warning messages that were previously
being logged during shader compilation.

0 files changed, 0 insertions, 0 deletions