serial: 8250: ASPEED_VUART: select REGMAP instead of depending on it

REGMAP is a hidden (not user visible) symbol. Users cannot set it
directly thru "make *config", so drivers should select it instead of
depending on it if they need it.

Consistently using "select" or "depends on" can also help reduce
Kconfig circular dependency issues.

Therefore, change the use of "depends on REGMAP" to "select REGMAP".

Fixes: 8d310c91 ("drivers/tty/serial/8250: Make Aspeed VUART SIRQ polarity configurable")
Cc: stable <stable@kernel.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Oskar Senft <osk@google.com>
Cc: linux-serial@vger.kernel.org
Link: https://lore.kernel.org/r/20230226053953.4681-9-rdunlap@infradead.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/Kconfig

@@ -257,8 +257,9 @@ config SERIAL_8250_ASPEED_VUART
 	tristate "Aspeed Virtual UART"
 	depends on SERIAL_8250
 	depends on OF
-	depends on REGMAP && MFD_SYSCON
+	depends on MFD_SYSCON
 	depends on ARCH_ASPEED || COMPILE_TEST
+	select REGMAP
 	help
 	  If you want to use the virtual UART (VUART) device on Aspeed
 	  BMC platforms, enable this option. This enables the 16550A-