ShellPkg/UefiShellDebug1: Return if ShellCommandLineParse() failed (3/4)

This patch aims to help breaking down the long functions present in
the ShellPkg and reduce complexity/nested code and conditions.

Return directly if ShellCommandLineParse() returned an error Status.
In such case, the "Package" that should be allocated by
ShellCommandLineParse() is already freed in:
ShellCommandLineParse()
\-ShellCommandLineParseEx()
\-InternalCommandLineParse()
so there is no need to free it with ShellCommandLineFreeVarList().

To avoid having one large commit updating all the UefiShellDebug1
commands, only update these files:
- MemMap.c
- Mm.c
- Mode.c
- Pci.c

No functional change should be induced by this patch.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>