Drop set_fs and get_fs since they are not present in kernel > 5.13.
Fix compilation warning:
/__w/openwrt/openwrt/openwrt/build_dir/target-mipsel-openwrt-linux-musl_musl/linux-bcm47xx_generic/broadcom-wl-5.10.56.27.3/driver/wl_iw.c: In function 'dev_wlc_ioctl':
/__w/openwrt/openwrt/openwrt/build_dir/target-mipsel-openwrt-linux-musl_musl/linux-bcm47xx_generic/broadcom-wl-5.10.56.27.3/driver/wl_iw.c:121:14: error: implicit declaration of function 'get_fs'; did you mean 'sget_fc'? [-Werror=implicit-function-declaration]
121 | fs = get_fs();
| ^~~~~~
| sget_fc
/__w/openwrt/openwrt/openwrt/build_dir/target-mipsel-openwrt-linux-musl_musl/linux-bcm47xx_generic/broadcom-wl-5.10.56.27.3/driver/wl_iw.c:121:14: error: incompatible types when assigning to type 'mm_segment_t' from type 'int'
/__w/openwrt/openwrt/openwrt/build_dir/target-mipsel-openwrt-linux-musl_musl/linux-bcm47xx_generic/broadcom-wl-5.10.56.27.3/driver/wl_iw.c:122:9: error: implicit declaration of function 'set_fs'; did you mean 'sget_fc'? [-Werror=implicit-function-declaration]
122 | set_fs(KERNEL_DS);
| ^~~~~~
| sget_fc
/__w/openwrt/openwrt/openwrt/build_dir/target-mipsel-openwrt-linux-musl_musl/linux-bcm47xx_generic/broadcom-wl-5.10.56.27.3/driver/wl_iw.c:122:16: error: 'KERNEL_DS' undeclared (first use in this function); did you mean 'KERNFS_NS'?
122 | set_fs(KERNEL_DS);
| ^~~~~~~~~
| KERNFS_NS
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
