staging: r8188eu: remove a variable

Check the result of rtw_check_bcn_info directly and remove the ret
variable.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20221126160129.178697-11-martin@kaiser.cx


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