Au1200: kill IDE driver function prototypes

Fix these warnings emitted when compiling drivers/ide/mips/au1xxx-ide.c:

include/asm/mach-au1x00/au1xxx_ide.h:137: warning: 'auide_tune_drive' declared 
`static' but never defined
include/asm/mach-au1x00/au1xxx_ide.h:138: warning: 'auide_tune_chipset' declared
 `static' but never defined

by wiping out the whole "function prototyping" section from the header file
<asm-mips/mach-au1x00/au1xxx_ide.h> as it mostly declared functions that are
already dead in the IDE driver; move the only useful prototype into the driver.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>