[llvm][ARM] Remove non-existent arm1176j-s CPU

This was removed in https://reviews.llvm.org/D52594 for clang.

The one test using it has been updated to use the mpcore
CPU as the linked clang change does.

This is part of fixing https://bugs.llvm.org/show_bug.cgi?id=50454.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D103022