This is a recommit of r336322, previously reverted in r336324 due to

a deficiency in TableGen that has been addressed in r336334.

[AArch64][SVE] Asm: Support for predicated FP rounding instructions.

This patch also adds instructions for predicated FP square-root and
reciprocal exponent.

The added instructions are:
- FRINTI  Round to integral value (current FPCR rounding mode)
- FRINTX  Round to integral value (current FPCR rounding mode, signalling inexact)
- FRINTA  Round to integral value (to nearest, with ties away from zero)
- FRINTN  Round to integral value (to nearest, with ties to even)
- FRINTZ  Round to integral value (toward zero)
- FRINTM  Round to integral value (toward minus Infinity)
- FRINTP  Round to integral value (toward plus Infinity)
- FSQRT   Floating-point square root
- FRECPX  Floating-point reciprocal exponent

llvm-svn: 336387