Update wl1251 firmware loading path

The wl1251 driver in upstream linux kernels expects its firmware files
to live at
  ti-connectivity/wl1251-fw.bin
  ti-connectivity/wl1251-nvs.bin
and the linux-firmware package uses the same names for these files.
However, our current (older) kernel still expects them to be named
  wl1251-fw.bin
  wl1251-nvs.bin
and so firmware loading would fail.

RescueOS v1.1 included these files under the older filenames, but we'd
like to use the official (upstream) names.  Patch our kernel to match.

Also remove the unnecessary (and now erroneous) firmware check from
setup-wpa-wifi.sh.

buildrootconfig

@@ -39,6 +39,7 @@ BR2_TARGET_ROOTFS_CRAMFS=y
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
 BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION="http://n900.quitesimple.org/rescueOS/sourcecode/kernel_source.tar.gz"
+BR2_LINUX_KERNEL_PATCH="../N900_RescueOS/kernel-patches/0001-net-wireless-wl1251-update-firmware-path.patch"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="../N900_RescueOS/kernel_config"
 BR2_LINUX_KERNEL_ZIMAGE=y