imx8m: fix cache setup for dynamic sdram size

the mem_map structure containing the size of SDRAM is used in various
cache functions in cache_v8.c thus we need to update it with the
sdram size the board is configured with as well. Without this
the cache functions do not get setup properly and can hang
in the case where a board reports more SDRAM than defined in
PHYS_SDRAM_SIZE.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>

arch/arm/mach-imx/imx8m/soc.c

@@ -210,6 +210,9 @@ int dram_init(void)
 	else
 		gd->ram_size = sdram_size;
 
+	/* also update the SDRAM size in the mem_map used externally */
+	imx8m_mem_map[5].size = sdram_size;
+
 #ifdef PHYS_SDRAM_2_SIZE
 	gd->ram_size += PHYS_SDRAM_2_SIZE;
 #endif