fix: replace strlcpy with preferred strscpy

Since it is preferred to use strscpy over strlcpy for its insecurity, update the only one line where it is used. This change also solves the build issue when GNU glibc cannot find strlcpy throwing the following error with recent environments:

8:26 iomz@sazanka:~/ghq/github.com/nns779/px4_drv/driver
[develop|✚1…2] ❯❯❯ make
make[1]: Entering directory '/usr/src/linux-headers-6.8.0-47-generic'
warning: the compiler differs from the one used to build the kernel
  The kernel was built by: x86_64-linux-gnu-gcc-13 (Ubuntu 13.2.0-23ubuntu4) 13.2.0
  You are using:           gcc-13 (Ubuntu 13.2.0-23ubuntu4) 13.2.0
  CC [M]  /home/iomz/ghq/github.com/nns779/px4_drv/driver/ptx_chrdev.o
/home/iomz/ghq/github.com/nns779/px4_drv/driver/ptx_chrdev.c: In function ‘ptx_chrdev_context_create’:
/home/iomz/ghq/github.com/nns779/px4_drv/driver/ptx_chrdev.c:569:9: error: implicit declaration of function ‘strlcpy’; did you mean ‘strscpy’? [-Werror=implicit-function-declaration]
  569 |         strlcpy(ctx->devname, devname, sizeof(ctx->devname));
      |         ^~~~~~~
      |         strscpy
/home/iomz/ghq/github.com/nns779/px4_drv/driver/ptx_chrdev.c: At top level:
/home/iomz/ghq/github.com/nns779/px4_drv/driver/ptx_chrdev.c:727:5: warning: no previous prototype for ‘ptx_chrdev_context_reserve’ [-Wmissing-prototypes]
  727 | int ptx_chrdev_context_reserve(struct ptx_chrdev_context *chrdev_ctx,
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:243: /home/iomz/ghq/github.com/nns779/px4_drv/driver/ptx_chrdev.o] Error 1
make[2]: *** [/usr/src/linux-headers-6.8.0-47-generic/Makefile:1925: /home/iomz/ghq/github.com/nns779/px4_drv/driver] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-6.8.0-47-generic'
make[1]: *** [Makefile:240: __sub-make] Error 2
make: *** [Makefile:19: px4_drv.ko] Error 2

cf. https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html

nns779 / px4_drv

fix: replace strlcpy with preferred strscpy #30