DbgValueHistoryCalculator: Ignore call instructions that claim to clobber SP.

The AArch64 backend marks calls that involve aggregate function
arguments as having an implicit def of SP. We already have the same
workaround in LiveDebugValues and in DbgValueHistoryCalculator for SP
clobbers in register masks. This adds register defs to the list.

Fixes rdar://problem/30361929 and Swift SR-3851.

llvm-svn: 304471