pc386: Improve boot command arguments for console/printk device selection

This patch adds the "--printk=" boot command line argument to specify
the printk() device. It also enhances the "--console=" boot command
line argument to match any device configured in the console device
table. The arguments are parsed as early as possible so they take
effect early. Currently, this is immediately after PCI initialization.

c/src/lib/libbsp/shared/console_private.h

@@ -7,7 +7,7 @@
  */
 
 /*
- *  COPYRIGHT (c) 1989-2011.
+ *  COPYRIGHT (c) 1989-2011, 2016.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -57,6 +57,16 @@ extern int bsp_com_inch(void);
  */
 int vt_ioctl( unsigned int cmd, unsigned long arg);
 
+/**
+ *  @brief console_initialize_data
+ *
+ *  This must be called before dynamic registration of devices can occur.
+ *  It is normally called as a side-effect of @a console_initialize() but
+ *  if a probe and dynamic registration occurs before that, then this method
+ *  should be explicitly invoked.
+ */
+void console_initialize_data(void);
+
 /**
  *  @brief console_register_devices
  *