ide: define MAX_HWIFS in <linux/ide.h>

* Now that ide_hwif_t instances are allocated dynamically
  the difference between MAX_HWIFS == 2 and MAX_HWIFS == 10
  is ~100 bytes (x86-32) so use MAX_HWIFS == 10 on all archs
  except these ones that use MAX_HWIFS == 1.

* Define MAX_HWIFS in <linux/ide.h> instead of <asm/ide.h>.

[ Please note that avr32/cris/v850 have no <asm/ide.h>
  and alpha/ia64/sh always define CONFIG_IDE_MAX_HWIFS. ]

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>