tools: kwboot: Fix parsing SDIO kwbimage

Despite the official specification, Marvell BootROM does not interpret
srcaddr from SDIO image as offset in number of sectors (like for SATA
image), but as offset in bytes (like for all other images except SATA).

To parse SDIO kwbimage in the same way as Marvell BootROM, it is needed to
interpret srcaddr in bytes. This change fixes loading of SDIO images via
kwboot over UART.

Fixes: 792e4235 ("tools: kwboot: Patch source address in image header")
Signed-off-by: Pali Rohár <pali@kernel.org>