This is based a patch by William Park <opengeometry@yahoo.ca> included in
2.6.10-mm1, in order to fix booting from usb-storage devices which no longer
make their partitions immediately available.

While William's patch fixed the situation where you boot from a "root=8:1"
parameter (to correspond to /dev/sda1), it does not allow you to use
"root=/dev/sda1" (which apparently worked in 2.6.9 and earlier), because
the name-->dev_t discovery is done before the "retry" loop starts, and is
not retried during the loop.

This patch, which replaces William's, solves the above problems.

Signed-off-by: Daniel Drake <dsd@gentoo.org>