asm-generic: add legacy I/O header files

The dma.h, hw_irq.h, serial.h and timex.h files originally
described PC-style i8237, i8259A, i8250, i8253 and i8255 chips
as well as the VGA style text mode graphics.

Modern architectures live happily without these specific
interfaces, but a few definitions from these headers keep
getting used in common code.

The new generic headers are what most architectures use
anyway nowadays, just implementing the minimal definitions.

Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/asm-generic/vga.h

@@ -0,0 +1,24 @@
+/*
+ *	Access to VGA videoram
+ *
+ *	(c) 1998 Martin Mares <mj@ucw.cz>
+ */
+#ifndef __ASM_GENERIC_VGA_H
+#define __ASM_GENERIC_VGA_H
+
+/*
+ *	On most architectures that support VGA, we can just
+ *	recalculate addresses and then access the videoram
+ *	directly without any black magic.
+ *
+ *	Everyone else needs to ioremap the address and use
+ *	proper I/O accesses.
+ */
+#ifndef VGA_MAP_MEM
+#define VGA_MAP_MEM(x, s) (unsigned long)phys_to_virt(x)
+#endif
+
+#define vga_readb(x) (*(x))
+#define vga_writeb(x, y) (*(y) = (x))
+
+#endif /* _ASM_GENERIC_VGA_H */