staging: r8188eu: move out assignment in if condition

Should not use assignment in if condition.

Signed-off-by: Marcelo Aloisio da Silva <marcelo.as@aol.com>
Link: https://lore.kernel.org/r/20220218040140.GA22796@snoopy


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