[TLI][AArch64] Add mappings to vectorized functions from ArmPL

Arm Performance Libraries contain math library which provides
vectorized versions of common math functions.
This patch allows to use it with clang and llvm via -fveclib=ArmPL or
-vector-library=ArmPL, so loops with such calls can be vectorized.
The executable needs to be linked with the amath library.

Arm Performance Libraries are available at:
https://developer.arm.com/Tools%20and%20Software/Arm%20Performance%20Libraries

Reviewed by: paulwalker-arm
Differential Revision: https://reviews.llvm.org/D154508