BaseTools: LzmaCompress: fix gcc-6 warning "misleading-indentation"

BaseTools: LzmaCompress: fix gcc-6 warning "misleading-indentation"

The way the first use of the "_maxMode" variable is commented out (i.e.,
together with the enclosing "if" statement) in GetOptimum() triggers the
"misleading-indentation" warning that is new in gcc-6.0, for the block of
code that originally depended on the "if" statement. Gcc believes
(mistakenly) that the programmer believes (mistakenly) that the block
depends on (repIndex == 0) higher up.

Restore the if statement, with a controlling expression that comprises the
constant 1 and "_maxMode" commented out.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Cole Robinson <crobinso@redhat.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Reported-by: Cole Robinson <crobinso@redhat.com>
Suggested-by: Jordan Justen <jordan.l.justen@intel.com>
Build-tested-by: Cole Robinson <crobinso@redhat.com>
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1307439
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>