zephyr: npcx: refactor the calculation of total RAM blcok
zephyr: npcx: refactor the calculation of total RAM blcok

The calculation of the total RAM blocks is determined by the size of
the code RAM, data RAM, and the RAM used by the booter. In the current
source, the RAM used by the booter is hardcoded. This CL replaces the
hardcoding by fetching the size from the DT node bootloader_ram.

BUG=none
BRANCH=none
TEST="zmake testall -clobber"
TEST="check the total RAM block is correct for different npcx variants"

Signed-off-by: Jun Lin <4865d89268068846db8afe2dcacc793288c792a0@nuvoton.com>
Change-Id: Ia04710360ec4d3144860fb1b33763e2230747c44
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3443081
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Reviewed-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@google.com>
Commit-Queue: CH Lin <49997681dc186e71092740314bf6c6feeca6e227@nuvoton.com>
Tested-by: CH Lin <49997681dc186e71092740314bf6c6feeca6e227@nuvoton.com>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec