Correct get_flash_region() to use inclusive upper bounds

get_flash_region() emits a struct flash_region, which uses chipoff_t for
the start and end addresses of a region. chipoff_t is defined as a valid
flash address, so it was wrong to be setting the end address to start +
len; this is clearly wrong in the case where there is a single region
because setting end to the flash size generates an address that is
beyond the end of the chip (due to zero-indexing).

This changes the one actual implementation of .get_region in ichspi.c to
use inclusive upper bounds, and corrects all callers of
get_flash_region() to treat the upper bounds as inclusive. Overall this
reduces complexity slightly by removing more downward adjustments by 1
than it needs to add upward adjustments.

TEST=on yaviks, `flashrom -V -x` prints equivalent messages about
     "x region (0xZZZZ..0xZZZZ) is readable" before and after this
     patch.

Change-Id: Ia0ca867aef33b598c2697fc264807fa5e29683ec
Signed-off-by: Peter Marheine <pmarheine@chromium.org>
---
M erasure_layout.c
M flashrom.c
M ichspi.c
3 files changed, 22 insertions(+), 22 deletions(-)