staging: r8188eu: Fix misspelling in comment "writting" -> "writing"

This patch fixes some spelling typo in error message reported by
checkpatch.pl

WARNING: 'writting' may be misspelled - perhaps 'writing'?

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Link: https://lore.kernel.org/r/1648636275-13558-1-git-send-email-baihaowen@meizu.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>