[PATCH] call_usermodehelper retval fix

[PATCH] call_usermodehelper retval fix

The reworked firmware loader in the DVB patches needs the fix to the
call_usermodehelper() return value.

From: Rusty Russell <rusty@rustcorp.com.au>

MODULE_ALIAS_BLOCK() and MODULE_ALIAS_CHAR() define aliases of form
"XXX-<major>-<minor>", so we should probe for modules using this form.
Unfortunately in 2.4, block aliases were "XXX-<major>" and char aliases
were of both forms.

Ideally, all modules would now be using MODULE_ALIAS() macros to define
their aliases, and the old configuration files wouldn't matter as much.
Unfortunately, this hasn't happened, so we make request_module() return the
exit status of modprobe, and then do fallback when probing for char and
block devices.

(Kudos to Chris Wright, I stole his kernel_thread flags).