UefiCpuPkg/PiSmmCpuDxeSmm: remove superfluous ENDs from NASM source

UefiCpuPkg/PiSmmCpuDxeSmm: remove superfluous ENDs from NASM source

Commits 28ee5816465b1 and 246cd9085f806 added these ENDs as part of the
manual conversion from *.asm files. However, the ENDs makes no sense for
NASM. Although they don't break the build, NASM complains about them:

  label alone on a line without a colon might be in error

(This NASM warning category dates back to NASM 0.95, commit
6768eb71d8deb.)

Remove the ENDs.

Cc: Jeff Fan <jeff.fan@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>