ANDROID: scsi_debug: Support configuring the maximum segment size

Add a kernel module parameter for configuring the maximum segment size.
This patch enables testing SCSI support for segments smaller than the
page size.

Bug: 261097222
Change-Id: I0600f5c7d3c8d45eaa0342c3eeecdefad476e213
Signed-off-by: Bart Van Assche <bvanassche@google.com>