configs: j7200: correct mmc offset

This patch corrects the MMC raw mode sector offset.

Current allocated size for tiboot3 is 1MB and 2MB for tispl.

Without this correct offset eMMC boot will fail.

Fixes: f8c1e893 (configs: j7200_evm_a72: Add Initial suppot)
Fixes: 02dff65e (configs: j7200_evm_r5: Add initial support)
Fixes: 360c7f46 (configs: Add configs for J7200 High Security EVM)

Way to test with eMMC boot from boot0/1 partition
Boot with SD card, copy images to eMMC boot0 or boot1 partition

=> mmc dev 0 (1 or 2)
=> fatload mmc 1 ${loadaddr} tiboot3.bin
=> mmc write ${loadaddr} 0x0 0x800
=> fatload mmc 1 ${loadaddr} tispl.bin
=> mmc write ${loadaddr} 0x800 0x1000
=> fatload mmc 1 ${loadaddr} u-boot.img
=> mmc write ${loadaddr} 0x1800 0x2000
=> mmc partconf 0 1 (1 or 2) 1
=> mmc bootbus 0 2 0 0

Cc: Bhavya Kapoor <b-kapoor@ti.com>
Cc: Diwakar Dhyani <d-dhyani@ti.com>
Cc: KEERTHY <j-keerthy@ti.com>
Signed-off-by: Udit Kumar <u-kumar1@ti.com>