[X86][SKX] Adding scheduling info of non-intrinsic + commutable SKX opcodes.

Updated the scheduling information of the SKX subtarget  in the file X86SchedSkylakeServer.td under lib/Target/X86 to:
1. add regular opcodes in addition to the suffixed "_Int" opcodes
2. add the (V)MAXCPD/MAXCPS/MAXCSD/MAXCSS/MINCPD/MINCPS/MINCSD/MINCSS
    instructions that are equivalent to their counterparts without the 'C' as they are part of a hack to
    make floating point min/max commutable under fast math.

Reviewers: zvi, RKSimon, craig.topper
Differential Revision: https://reviews.llvm.org/D39833

Change-Id: Ie13702a5ce1b1a08af91ca637a52b6962881e7d6
llvm-svn: 318024