aspeed: Support create flash devices via command line for AST1030 Add a "if-statement" in aspeed_minibmc_machine_init function. If users add "-nodefaults" in command line, the flash devices should be created by users setting. Otherwise, the flash devices are created at machine init. Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> Reviewed-by: Cédric Le Goater <clg@redhat.com>