o Mount the EFI file system as msdosfs and not ufs as it's a FAT
file system. Introduce Mount_msdos() for this to go side-by-side
with Mount().
o Also, since mounting is performed as a command (which means it's
queued, sorted, lost, found and executed), we cannot create a
directory on the file system by calling mkdir. We must make sure
the mkdir happens after the mount. Introduce Mkdir_command() to
allow mkdir operations to be queued, sorted, lost, found and
executed as well.
Approved by: re (jhb, rwatson)
7e8dbd8b20