boards: variscite: imx8mp_var_som: Update index.rst

Update Cortex-M7 DDR address in memory mapping table to 0x7B000000.

Signed-off-by: Andre Morishita <andre.m@variscite.com>

Author: morishitaandre

boards/variscite/imx8mp_var_som/doc/index.rst

@@ -148,7 +148,7 @@ supported: ITCM and DDR). These are the memory mapping for A53 and M7:
 +------------+-------------------------+------------------------+-----------------------+----------------------+
 | OCRAM_S    | 0x00180000-0x00188FFF   | 0x20180000-0x20188FFF  | 0x00180000-0x00188FFF | 36KB                 |
 +------------+-------------------------+------------------------+-----------------------+----------------------+
-| DDR        | 0x80000000-0x803FFFFF   | 0x7E200000-0x7E3FFFFF  | 0x7E000000-0x7E1FFFFF | 2MB                  |
+| DDR        | 0x80000000-0x803FFFFF   | 0x7B200000-0x7B3FFFFF  | 0x7B000000-0x7B1FFFFF | 2MB                  |
 +------------+-------------------------+------------------------+-----------------------+----------------------+
 
 For more information about memory mapping see the