The size of the flash write buffer should be rounded
down to the multiply of flash page size.
Using write chunks of unadjusted size results in write of chunks
unaligned to flash pages.
Change-Id: If7931362ee193dff4dc2df7ec78f13530658cf08
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/7187
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>