smsc911x: request_any_context_irq can return postive value upon success

When support for nested interrupts was merged in commit
3a076852dc80aa3cfc02c880c41dcd947cdeab70 in kernel 2.6.38 it appears as
though this previous commit was not merged properly.

Change-Id: I2aca73fdb1ae663ca058aadd27fe658de6d851e3
Signed-off-by: Terence Hampson <thampson@codeaurora.org>