This patch extends the PredicateMethod of AsmOperands used in SVE's
LD1 instructions with a DiagnosticPredicate. This makes them 'context
sensitive' to the operand that has been parsed and tells the user to
use the right register (with expected shift/extend), rather than telling
the immediate is out of range when it actually parsed a register.
Patch [2/2] in a series to improve assembler diagnostics for SVE:
- Patch [1/2]: https://reviews.llvm.org/D45879
- Patch [2/2]: https://reviews.llvm.org/D45880