vl: remove dead code in parse_memory_options()
mem_str will never be an empty string, because qemu_opt_get_size() fails
if it encounters one:
$ ./qemu-system-x86_64 -m size=
qemu-system-x86_64: -m size=: Parameter size expects a non-negative number below 2^64
Optional suffix k, M, G, T, P or E means kilo-, mega-, giga-, tera-, peta-
and exabytes, respectively.
Suggested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>