bootutil: sector size == padding size?

[jorgenmk]

https://github.com/mcu-tools/mcuboot/blob/main/boot/bootutil/src/bootutil_misc.c#L524

Here the padding size is assumed to always be the same as sector size, is this correct?

We are running into issues when application starts filling up the partition.

For example, try to build and run sdk-nrf/applications/connectivity_bridge for board thingy91x/nrf5340/cpuapp. This goes very wrong runtime.

Forcing padding_sz to 512 (default CONFIG_PM_PARTITION_SIZE_MCUBOOT_PAD) makes it work again.

@taltenbach