CodeGen: Use MachineInstr& in TargetInstrInfo, NFC

This is mostly a mechanical change to make TargetInstrInfo API take
MachineInstr& (instead of MachineInstr* or MachineBasicBlock::iterator)
when the argument is expected to be a valid MachineInstr.  This is a
general API improvement.

Although it would be possible to do this one function at a time, that
would demand a quadratic amount of churn since many of these functions
call each other.  Instead I've done everything as a block and just
updated what was necessary.

This is mostly mechanical fixes: adding and removing `*` and `&`
operators.  The only non-mechanical change is to split
ARMBaseInstrInfo::getOperandLatencyImpl out from
ARMBaseInstrInfo::getOperandLatency.  Previously, the latter took a
`MachineInstr*` which it updated to the instruction bundle leader; now,
the latter calls the former either with the same `MachineInstr&` or the
bundle leader.

As a side effect, this removes a bunch of MachineInstr* to
MachineBasicBlock::iterator implicit conversions, a necessary step
toward fixing PR26753.

Note: I updated WebAssembly, Lanai, and AVR (despite being
off-by-default) since it turned out to be easy.  I couldn't run tests
for AVR since llc doesn't link with it turned on.

llvm-svn: 274189
diff --git a/llvm/lib/Target/ARM/ARMScheduleA9.td b/llvm/lib/Target/ARM/ARMScheduleA9.td
index 9a1d222..519e595 100644
--- a/llvm/lib/Target/ARM/ARMScheduleA9.td
+++ b/llvm/lib/Target/ARM/ARMScheduleA9.td
@@ -2025,12 +2025,12 @@
 
 // Define a predicate to select the LDM based on number of memory addresses.
 def A9LMAdr#NumAddr#Pred :
-  SchedPredicate<"(TII->getNumLDMAddresses(MI)+1)/2 == "#NumAddr>;
+  SchedPredicate<"(TII->getNumLDMAddresses(*MI)+1)/2 == "#NumAddr>;
 
 } // foreach NumAddr
 
 // Fall-back for unknown LDMs.
-def A9LMUnknownPred : SchedPredicate<"TII->getNumLDMAddresses(MI) == 0">;
+def A9LMUnknownPred : SchedPredicate<"TII->getNumLDMAddresses(*MI) == 0">;
 
 // LDM/VLDM/VLDn address generation latency & resources.
 // Dynamically select the A9WriteAdrN sequence using a predicate.