rtas_flash: fix blockCnt iteration

for (blockCnt = 0; blockCnt <= FLASHSIZE; blockCnt += FLASH_BLOCK_SIZE)
will iterate more than FLASHSIZE, thus causing overwriting. Change <= to
< to limit block count correctly.

Signed-off-by: Minsoo Choo <minsoo@minsoo.io>
Message-ID: <20260520220212.525-3-minsoo@minsoo.io>
Signed-off-by: Thomas Huth <th.huth@posteo.eu>