Fix basename() implicit declaration

While compiling yafut in OpenWrt GCC will print:

[26/31] Building C object CMakeFiles/yafut.dir/src/mtd.c.o /home/robimarko/Building/RB5009/openwrt/build_dir/target-aarch64_cortex-a72_musl/yafut-2024.05.13~290b7580/src/mtd.c: In function 'read_oobavail_from_sysfs': /home/robimarko/Building/RB5009/openwrt/build_dir/target-aarch64_cortex-a72_musl/yafut-2024.05.13~290b7580/src/mtd.c:128:24: warning: implicit declaration of function 'basename' [-Wimplicit-function-declaration]
  128 |                        basename(strdup(mtd_path)));
      |                        ^~~~~~~~
/home/robimarko/Building/RB5009/openwrt/build_dir/target-aarch64_cortex-a72_musl/yafut-2024.05.13~290b7580/src/mtd.c:127:61: warning: format '%s' expects argument of type 'char *', but argument 4 has type 'int' [-Wformat=]
  127 |         ret = snprintf(path, sizeof(path), "/sys/class/mtd/%s/oobavail",
      |                                                            ~^
      |                                                             |
      |                                                             char *
      |                                                            %d
  128 |                        basename(strdup(mtd_path)));
      |                        ~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                        |
      |                        int
[31/31] Linking C executable yafut

It will somehow still compile, but trying to use yafut on the device will lead to instant Segmentation fault.

So, lets simply include the required header that provides basename.

Fixes: #23

kempniu / yafut

Fix basename() implicit declaration #24