sample: fix compiler warning

/usr/include/x86_64-linux-gnu/bits/stdio2.h:86:10: warning: ‘value’ may be used uninitialized [-Wmaybe-uninitialized]
   86 |   return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, __va_arg_pack ());
      |          ^
sample.c: In function ‘main’:
sample.c:45:13: note: ‘value’ was declared here
   45 |         int value, ret = -1;
      |             ^

libPCSCv2part10/sample.c

@@ -42,7 +42,7 @@ int main(void)
  LONG rv;
  SCARDCONTEXT hContext;
  SCARDHANDLE hCard;
- int value, ret = -1;
+ int value = -1, ret = -1;
  DWORD dwReaders, dwPref;
  char *mszReaders;