USB: gadget: ci13xxx: don't assume that PAGE_SIZE is 4096

Page size for transaction descriptors for CI13XXX has nothing
common with page size from MM. Using platform and configuration
specific PAGE_SIZE is wrong.

Signed-off-by: Artem Leonenko <tikkeri@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>