[X86][BtVer2] Fix latency/throughput of scalar integer MUL instructions.

Single operand MUL instructions that implicitly set EAX have the following
latency/throughput profile (see below):

imul %cl              # latency: 3cy - uOPs: 1 - 1 JMul
imul %cx              # latency: 3cy - uOPs: 3 - 3 JMul
imul %ecx             # latency: 3cy - uOPs: 2 - 2 JMul
imul %rcx             # latency: 6cy - uOPs: 2 - 4 JMul

mul %cl               # latency: 3cy - uOPs: 1 - 1 JMul
mul %cx               # latency: 3cy - uOPs: 3 - 3 JMul
mul %ecx              # latency: 3cy - uOPs: 2 - 2 JMul
mul %rcx              # latency: 6cy - uOPs: 2 - 4 JMul

Excluding the 64bit variant, which has a latency of 6cy, every other instruction
has a latency of 3cy. However, the number of decoded macro-opcodes (as well as
the resource cyles) depend on the MUL size.

The two operand MULs have a more predictable profile (see below):

imul %dx, %dx         # latency: 3cy - uOPs: 1 - 1 JMul
imul %edx, %edx       # latency: 3cy - uOPs: 1 - 1 JMul
imul %rdx, %rdx       # latency: 6cy - uOPs: 1 - 4 JMul

imul $3, %dx, %dx     # latency: 4cy - uOPs: 2 - 2 JMul
imul $3, %ecx, %ecx   # latency: 3cy - uOPs: 1 - 1 JMul
imul $3, %rdx, %rdx   # latency: 6cy - uOPs: 1 - 4 JMul

This patch updates the values in the Jaguar scheduling model and regenerates
llvm-mca tests.

Differential Revision: https://reviews.llvm.org/D66547

llvm-svn: 369661