lib/uuid.c: use unique name for PARTITION_SYSTEM_GUID

lib/uuid.c: use unique name for PARTITION_SYSTEM_GUID

The name defined for PARTITION_SYSTEM_GUID in list_guid[] depends on
configuration options. It is "system" if CONFIG_PARTITION_TYPE_GUID is
enabled or "System Partition" if CONFIG_CMD_EFIDEBUG or CONFIG_EFI are
enabled. In addition, the unit test in test/common/print.c is incorrect
because it expects only "system" (or a hex GUID).

Make things more consistent by using a clear and unique name: "EFI
System Partition" whatever the configuration, and update the unit test
accordingly.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>