[console] Allow usage to be defined independently for each console

Add the concept of a "console usage", such as "standard output" or
"debug messages".  Allow usages to be associated with each console
independently.  For example, to send debugging output via the serial
port, while preventing it from appearing on the local console:

  #define CONSOLE_SERIAL CONSOLE_USAGE_ALL
  #define CONSOLE_PCBIOS ( CONSOLE_USAGE_ALL & ~CONSOLE_USAGE_DEBUG )

If no usages are explicitly specified, then a default set of usages
will be applied.  For example:

  #define CONSOLE_SERIAL

will have the same affect as

  #define CONSOLE_SERIAL CONSOLE_USAGE_ALL

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/efi/efi_console.c

@@ -23,6 +23,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <ipxe/efi/efi.h>
 #include <ipxe/ansiesc.h>
 #include <ipxe/console.h>
+#include <config/console.h>
 
 #define ATTR_BOLD		0x08
 
@@ -48,6 +49,12 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #define ATTR_DEFAULT		ATTR_FCOL_WHITE
 
+/* Set default console usage if applicable */
+#if ! ( defined ( CONSOLE_EFI ) && CONSOLE_EXPLICIT ( CONSOLE_EFI ) )
+#undef CONSOLE_EFI
+#define CONSOLE_EFI CONSOLE_USAGE_ALL
+#endif
+
 /** Current character attribute */
 static unsigned int efi_attr = ATTR_DEFAULT;
 
@@ -273,4 +280,5 @@ struct console_driver efi_console __console_driver = {
 	.putchar = efi_putchar,
 	.getchar = efi_getchar,
 	.iskey = efi_iskey,
+	.usage = CONSOLE_EFI,
 };