uefi: Implement the new magenta_framebuffer instead of board_framebuffer.

The framebuffer should generally be abstracted behind the "display" object and
not exposed directly as part of the public board API. This change makes the
UEFI board use the magenta_framebuffer callback instead, who's purpose is more
explicit, which is separated from the board_* functions, and which will
hopefully go away at some point in the future.

Change-Id: I68fed541448096019b99712d901ea4a01e32e411
diff --git a/src/drivers/board/uefi/board.c b/src/drivers/board/uefi/board.c
index 7da00ae..9843365 100644
--- a/src/drivers/board/uefi/board.c
+++ b/src/drivers/board/uefi/board.c
@@ -24,6 +24,7 @@
 
 #include "base/init_funcs.h"
 #include "base/list.h"
+#include "boot/magenta.h"
 #include "drivers/blockdev/uefi.h"
 #include "drivers/board/board.h"
 #include "drivers/board/board_helpers.h"
@@ -50,8 +51,13 @@
 
 PUB_STAT(power, &uefi_power_ops)
 
-PUB_DYN(framebuffer, new_uefi_framebuffer())
-PUB_DYN(display, &new_fb_display(board_framebuffer(), NULL)->ops)
+PRIV_DYN(framebuffer, new_uefi_framebuffer())
+PUB_DYN(display, &new_fb_display(get_framebuffer(), NULL)->ops)
+
+FrameBufferOps *magenta_framebuffer(void)
+{
+	return get_framebuffer();
+}
 
 static int board_setup(void)
 {