vgabios: Move initialization code to new file vgainit.c.

Move the initialization code out of vgabios.c to a new file to reduce
the size of the vgabios.c file.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/Makefile b/Makefile
index 59aae99..8a3c9d1 100644
--- a/Makefile
+++ b/Makefile
@@ -202,7 +202,8 @@
 
 # VGA src files
 SRCVGA=src/output.c src/string.c src/hw/pci.c src/hw/serialio.c \
-    vgasrc/vgabios.c vgasrc/vgafb.c vgasrc/vgafonts.c vgasrc/vbe.c \
+    vgasrc/vgainit.c vgasrc/vgabios.c vgasrc/vgafb.c \
+    vgasrc/vgafonts.c vgasrc/vbe.c \
     vgasrc/stdvga.c vgasrc/stdvgamodes.c vgasrc/stdvgaio.c \
     vgasrc/clext.c vgasrc/bochsvga.c vgasrc/geodevga.c