vvfat: mark various functions as coroutine_fn

vvfat: mark various functions as coroutine_fn

Functions that can do I/O are prime candidates for being coroutine_fns.  Make the
change for those that are themselves called only from coroutine_fns.

In addition, coroutine_fns should do I/O using bdrv_co_*() functions, for
which it is required to hold the BlockDriverState graph lock.  So also nnotate
functions on the I/O path with TSA attributes, making it possible to
switch them to use bdrv_co_*() functions.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230309084456.304669-2-pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>