scoop: fix access to registers from second instance

Second instance of scoop contains registers shifted to 0x40 from the start
of the page. Instead of messing with register mapping, just limit register
address to 0x00..0x3f.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
