[builtins] Fix assembly in arm sync-ops.h
[builtins] Fix assembly in arm sync-ops.h

This assembly is part of a macro that was reformatted in D60351.
The missing space between push and { results in:

    Error: bad instruction `push{r4, r5,r6,lr}'

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@365957 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt