sys_fs & VFS: Misc bug fixes

[brian218]

1. Do not mount dev_usbXXX if its path is not properly specified since this can cause confusion to some games that detect and determine which USB flash drive to use.
2. Allow dev_usbXXX to be mounted, unmounted, and formatted(newfs) by the corresponding sys_fs syscalls as some games do format the attached USB flash drives in some cases.
3. Improve the permission check for the three syscalls mentioned above: PS3 root permission is required in order to perform actions on devices other than dev_usbXXX.
4. Add read-only flag check to sys_fs_newfs() to prevent devices with this flag from being formatted.
5. Implement CELL_FS_PATH path-as-device support.

[elad335]

I rather not adding new lv2_obj::sleep calls, I know it's like other syscalls, but its placemrnt is questinable in many places.

[brian218]

I rather not adding new lv2_obj::sleep calls, I know it's like other syscalls, but its placemrnt is questinable in many places.

How about ppu.state += cpu_flag::wait?

[elad335]

That statement is okay.