Staging: wilc1000: fix spelling mistake.

This patch corrects the spelling of the word function by adding missing
letter.
Problem found by checkpatch.pl :
CHECK: 'funcion' may be misspelled - perhaps 'function'?

Signed-off-by: Aybuke Ozdemir <aybuke.147@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>