net: Add noinline to reduce dev_ethtool stack size

Maximum stack size for arm32 devices is (configured by FRAME_WARN)
1024.  dev_ethtool()'s stacksize (=1208) exceeds this limit.

Adding noinline attribute to reduce stack size.

Change-Id: I00dbd3cad029ca99694d7cee611d4ee32016f889
Signed-off-by: Tejaswi Tanikella <tejaswit@codeaurora.org>