drivers/scsi/atp870u.c: fix bad use of udelay

drivers/scsi/atp870u.c: fix bad use of udelay

The ACARD driver calls udelay() with a value > 2000, which leads to to
the following compilation error on ARM:

  ERROR: "__bad_udelay" [drivers/scsi/atp870u.ko] undefined!
  make[1]: *** [__modpost] Error 1

This is because udelay is defined on ARM, roughly speaking, as

	#define udelay(n) ((n) > 2000 ? __bad_udelay() : \
		__const_udelay((n) * ((2199023U*HZ)>>11)))

The argument to __const_udelay is the number of jiffies to wait divided
by 4, but this does not work unless the multiplication does not
overflow, and that is what the build error is designed to prevent.  The
intended behavior can be achieved by using mdelay to call udelay
multiple times in a loop.

[[email protected]: adding context]
Signed-off-by: Martin Michlmayr <[email protected]>
Signed-off-by: Jonathan Nieder <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>