RISC-V: Improve vectorization of Match.sqrt() on floats

JDK-8190800 added `VSqrtF` and `SqrtF` nodes to support the vectorization of Match.sqrt() on floats. For riscv port, however, the scalar version of `sqrtF` still uses the old match rule that converts Float to Double first. It can be simplified to just use `SqrtF`.

The old match rule also affects the vectorization of Math.sqrt() on float. The current implementation will convert float to double with `vcvtFtoD`, then do `vsqrtD`, and then convert the result back to float with `vcvtDtoF`. If we use the new `SqrtF` match rule, it will only use `vsqrtF` to do the conversion. Take the test (Sqrt.java) from JDK-8190800 as an example:

before:

```
19a loadV V1, [R13] # vector (rvv)
1a2 vcvtFtoD V2, V1
1ae vfsqrt.v V1, V2 #@vsqrtD
1b6 vcvtDtoF V1, V1
1c2 storeV [R14], V1 # vector (rvv)
```

after:
```
1be loadV V1, [R12] # vector (rvv)
1c6 vfsqrt.v V1, V1 #@vsqrtF
1ce addi R12, R29, #144 # ptr, #@addP_reg_imm
1d2 storeV [R12], V1 # vector (rvv)
```