ubifs-utils: journal: Include <sys/stat.h>

ubifs-utils: journal: Include <sys/stat.h>

Include the <sys/stat.h> header file to fix the following error
when building with musl:

| ../git/ubifs-utils/libubifs/journal.c: In function 'ubifs_get_dent_type':
| ../git/ubifs-utils/libubifs/journal.c:414:24: error: 'S_IFMT' undeclared (first use in this function)
|   414 |         switch (mode & S_IFMT) {
|       |                        ^~~~~~
| ../git/ubifs-utils/libubifs/journal.c:414:24: note: each undeclared identifier is reported only once for each function it appears in
| ../git/ubifs-utils/libubifs/journal.c:415:14: error: 'S_IFREG' undeclared (first use in this function)
|   415 |         case S_IFREG:

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>