Add stub headers to support ext4l filesystem compilation:
New headers:
- bit_spinlock.h: bit-based spinlock stubs
- blkdev.h: block device structures and operations
- buffer_head.h: buffer head management with state functions
- crc32c.h: CRC32C checksum stub
- fs.h: filesystem structures (super_block, inode operations)
- journal-head.h: journal buffer head structure
- mutex.h: mutex stubs
Updates to existing headers:
- compat.h: add rcu_head callback structure
- jbd2.h: add wait.h and init.h includes for types
- sched.h: add current task stub
- workqueue.h: fix flush_work macro warning
These provide the minimal Linux kernel interfaces needed for
ext4 code to compile in U-Boot's single-threaded environment.
Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>
166dcda718