ANDROID: block: Add support for filesystem requests and small segments

Add support in the bio splitting code and also in the bio submission code
for bios with segments smaller than the page size.

Bug: 261097222
Change-Id: Icf1d7c3141bd31cc6630a0cecaf323b6f3318853
Signed-off-by: Bart Van Assche <bvanassche@google.com>