staging: mt7621-pci: Add spaces around '<<'

Add spaces around '<<' to fix checkpatch issue.
CHECK: spaces preferred around that '<<' (ctx:VxV)

Signed-off-by: Mamta Shukla <mamtashukla555@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>