USB: host: mark const variable tables as "const"

Mark the tables as const so that they end up in .rodata
section and don't cacheline share with things that get
written to.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Cc: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>