[llvm] RuntimeLibcalls: Add sqrtf to the Hexagon runtime libcall set (PR #210909)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > The patch looks good. Please add a small testcase to demonstrate the fact that hexagon_sqrtf is called instead of sqrtf.
> 
> That is what the existing tests cover

Though that seems to only be covered for fast math, which is not great test coverage. But still a general maintenance issue not changed by this patch 

https://github.com/llvm/llvm-project/pull/210909