usb/storage: redefine US_BULK_FLAG_IN and use it

US_BULK_FLAG_IN is defined as 1 and not used. The USB storage spec says
that bit 7 of flags within CBW defines the data direction. 1 is DATA-IN
(read from device) and 0 is the DATA-OUT. Bit 6 is obselete and bits 0-5
are reserved.
This patch redefines the unsued define US_BULK_FLAG_IN from 1 to 1 << 7
aka 0x80 and replaces the obvious users. In a following patch the
storage gadget will use it as well.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>