Eliminate more __must_check madness.

The return code from device_for_each_child() depends on the values
which the helper function returns.  If the helper function always
returns zero, it's utterly pointless to check the return code from
device_for_each_child().

The only code which knows if the return value should be checked is
the caller itself, so forcing the return code to always be checked
is silly.  Hence, remove the __must_check annotation.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>