iprowifi4965: fixed firmware filename for iwn6000g2afw.

see #10197
VM: vm_memset_physical(): Correct length parameter type
VFS: Fix broken zero_pages()

Besides that it failed to actually iterate through the vectors, it
shouldn't try to clear physical memory in the first place. The iovecs
refer to virtual address ranges. Rename it to zero_iovecs() to avoid
confusion.
IORequest::_CopyData(): Small optimization

If we're running in the context of the user team the I/O buffer belongs
to, we can use _CopySimple() as well.
IORequest: Add ClearData()
IORequest::Init(): Assert offset >= 0

Just to make sure we catch sparse file vectors that shouldn't be passed
here.
do_iterative_fd_io_iterate(): Support sparse files

* Check whether the vectors we get are sparse file vectors and satisfy
  them immediately instead of creating a subrequest. Untested, since the
  API isn't used by ext2 as it should be.
* Add error == B_OK to the condition of the outer loop.
ext2: ExtentStream::FindBlock(): Restructure/fix

* The binary search was somewhat broken.
* Restructure a bit so that only the binary/linear search itself is
  handled separately. The handling afterwards is common again.
* Fix sparse block handling:
  - There can be sparse blocks before the first extend.
  - Set the return parameter _count in this case as well.
  - Set the return parameter block to 0 instead of 0xffffffff. That's
    what ext2_get_file_map() expects.

Fixes an infinite loop in ext2_get_file_map() when sparse blocks are
involved, due to previously returning a wrong block and a 0 count.
Ticket #9274 may be related.
ext2_get_file_map(): Fix broken termination condition
ext2: Fix enabling/disabling the file cache

* Inode:
  - Rename {Enable,Disable}FileCache() to {Create,Delete}FileCache()
    and IsFileCacheDisabled() to HasFileCache(), since that is what they
    actually do. DeleteFileCache() now also sets the attributes to NULL,
    which makes fCached superfluous.
  - Introduce {Enable,Disable}FileCache(), which actually enable/disable
    the file cache. Use those methods for handling O_NOCACHE.
* ext2_free_cookie(): Reenable the file cache in case of O_NOCACHE.

Fixes crash when O_NOCACHE was used, since the file cache was deleted
without clearing the attribute and Inode::ReadAt() would use the deleted
object afterward.