[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 

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