unify bits/stat.h for all archs sharing a common definition

future archs should not define their own bits/stat.h but use this
generic one.

arch/loongarch64/bits/stat.h

@@ -1,18 +0,0 @@
-struct stat {
-	dev_t st_dev;
-	ino_t st_ino;
-	mode_t st_mode;
-	nlink_t st_nlink;
-	uid_t st_uid;
-	gid_t st_gid;
-	dev_t st_rdev;
-	unsigned long long __pad;
-	off_t st_size;
-	blksize_t st_blksize;
-	int __pad2;
-	blkcnt_t st_blocks;
-	struct timespec st_atim;
-	struct timespec st_mtim;
-	struct timespec st_ctim;
-	unsigned __unused[2];
-};

arch/riscv32/bits/stat.h

@@ -1,18 +0,0 @@
-struct stat {
-	dev_t st_dev;
-	ino_t st_ino;
-	mode_t st_mode;
-	nlink_t st_nlink;
-	uid_t st_uid;
-	gid_t st_gid;
-	dev_t st_rdev;
-	unsigned long long __pad;
-	off_t st_size;
-	blksize_t st_blksize;
-	int __pad2;
-	blkcnt_t st_blocks;
-	struct timespec st_atim;
-	struct timespec st_mtim;
-	struct timespec st_ctim;
-	unsigned __unused[2];
-};

arch/riscv64/bits/stat.h

@@ -1,18 +0,0 @@
-struct stat {
-	dev_t st_dev;
-	ino_t st_ino;
-	mode_t st_mode;
-	nlink_t st_nlink;
-	uid_t st_uid;
-	gid_t st_gid;
-	dev_t st_rdev;
-	unsigned long long __pad;
-	off_t st_size;
-	blksize_t st_blksize;
-	int __pad2;
-	blkcnt_t st_blocks;
-	struct timespec st_atim;
-	struct timespec st_mtim;
-	struct timespec st_ctim;
-	unsigned __unused[2];
-};