ARM: make libcall setup more table driven

Rather than create a series of function calls to setup the library calls, create
a table with the information and just use the table to drive the configuration
of the library calls.  This makes it easier to both inspect the list as well as
to modify it.  NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209089 91177308-0d34-0410-b5e6-96231b3b80d8