sim: Remove trailing dot when assigning a master's name

sim: Remove trailing dot when assigning a master's name

This patch fixes the master's name allocation in the system. The error
was occurring when a submaster was not specified in getMasterId: a
trailing separation dot was still added to the master's name.

Change-Id: I0e67900f6fdd36a61900453b55219fc7007d1b05
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10301
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>