armv8: fsl-layerscale: Rewrite reserving memory for MC and debug server

MC and debug server are not board-specific. Move reserving memory to SoC
file, using the new board_reserve_ram_top function. Reduce debug server
memory by 2MB to make room for secure memory.

In the system with MC and debug server, the top of u-boot memory
is not the end of memory. PRAM is not used for this reservation.

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/README b/README
index 4aa2aae..43f307f 100644
--- a/README
+++ b/README
@@ -5056,8 +5056,8 @@
 - CONFIG_SYS_DEBUG_SERVER_DRAM_BLOCK_MIN_SIZE
 	Define minimum DDR size required for debug server image
 
-- CONFIG_SYS_MEM_TOP_HIDE_MIN
-	Define minimum DDR size to be hided from top of the DDR memory
+- CONFIG_SYS_MC_RSV_MEM_ALIGN
+	Define alignment of reserved memory MC requires
 
 Reproducible builds
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