Also keep size override by FLASHSIZE Tcl variable possible. Partially backported from former upstream rp2040.c Signed-off-by: Tomas Vanek <vanekt@fbl.cz> Change-Id: I224c3644450e8b46e35714bfc5436219ffdee563 Reviewed-on: https://review.openocd.org/c/openocd/+/8451 Tested-by: jenkins