intel: Fix some theoretical buffer overflow

Looks to me like the theoretical max the sprintf()s need
here is about 34+4+9+sizeof(de->d_name) bytes. Let's just
make that 64+sizeof(de->d_name) for simplicity.

This shuts up the compiler:
../src/intel_device.c: In function ‘__intel_open_device__pci’:
../src/intel_device.c:387:60: warning: ‘%s’ directive writing up to 255 bytes into a region of size 247 [-Wformat-overflow=]
  387 |                         sprintf(path + base + 4, "/dev/dri/%s", de->d_name);
      |                                                            ^~
../src/intel_device.c:387:25: note: ‘sprintf’ output between 10 and 265 bytes into a destination of size 256
  387 |                         sprintf(path + base + 4, "/dev/dri/%s", de->d_name);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/intel_device.c:392:54: warning: ‘/dev’ directive writing 4 bytes into a region of size between 0 and 255 [-Wformat-overflow=]
  392 |                         sprintf(path + base + 3, "/%s/dev", de->d_name);
      |                                                      ^~~~
../src/intel_device.c:392:25: note: ‘sprintf’ output between 6 and 261 bytes into a destination of size 256
  392 |                         sprintf(path + base + 3, "/%s/dev", de->d_name);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

src/intel_device.c

@@ -335,9 +335,9 @@ static int __intel_open_device__major_minor(int _major, int _minor)
 static int __intel_open_device__pci(const struct pci_device *pci)
 {
 	struct stat st;
-	char path[256];
-	DIR *dir;
 	struct dirent *de;
+	char path[64+sizeof(de->d_name)];
+	DIR *dir;
 	int base;
 	int fd;