serial: 8250: SERIAL_8250_ASPEED_VUART should depend on ARCH_ASPEED

The Aspeed Virtual UART is only present on Aspeed BMC platforms.  Hence
add a dependency on ARCH_ASPEED, to prevent asking the user about this
driver when configuring a kernel without Aspeed BMC support.
Reviewed-by: NJeremy Kerr <jk@ozlabs.org>
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/259138c372d433005b4871789ef9ee8d15320307.1657528861.git.geert+renesas@glider.beSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/Kconfig

@@ -254,6 +254,7 @@ config SERIAL_8250_ASPEED_VUART
 	depends on SERIAL_8250
 	depends on OF
 	depends on REGMAP && MFD_SYSCON
+	depends on ARCH_ASPEED || COMPILE_TEST
 	help
 	  If you want to use the virtual UART (VUART) device on Aspeed
 	  BMC platforms, enable this option. This enables the 16550A-