[PowerPC] [NFC] Add test cases to the ISD::BR_CC node in the instruction selection

Add the following test case for the ISD::BR_CC node in the instruction selection
define i64 @testi64slt(i64 %c1, i64 %c2, i64 %c3, i64 %c4, i64 %a1, i64 %a2) #0 {
entry:
  %cmp1 = icmp eq i64 %c3, %c4
  %cmp3tmp = icmp eq i64 %c1, %c2
  %cmp3 = icmp slt i1 %cmp3tmp, %cmp1
  br i1 %cmp3, label %iftrue, label %iffalse
iftrue:
  ret i64 %a1
iffalse:
  ret i64 %a2
}
The data type i64 can be replaced by i32, i64, float, double

And condition codes can be replaced by: SETEQ, SETEN, SELT, SETLE, SETGT, SETGE,SETULT, SETULE, SSETGT, and SETUGE

Reviewed By: steven.zhang

Differential Revision: https://reviews.llvm.org/D54824

llvm-svn: 347828