aarch64: fix DRAM_MEM_END in layout.rs
According to the definition, DRAM_MEM_MAX_SIZE should be 1024G. Let's
remove the DRAM_MEM_END and just leave DRAM_MEM_MAX_SIZE.
/// Start of RAM on 64 bit ARM.
pub const DRAM_MEM_START: u64 = 0x8000_0000; // 2 GB.
-/// The maximum addressable RAM address.
-pub const DRAM_MEM_END: u64 = 0x00FF_8000_0000; // 1024 - 2 = 1022 GB.
/// The maximum RAM size.
-pub const DRAM_MEM_MAX_SIZE: u64 = DRAM_MEM_END - DRAM_MEM_START;
+pub const DRAM_MEM_MAX_SIZE: u64 = 0x00FF_8000_0000; // 1024 - 2 = 1022G.
/// Kernel command line maximum size.
/// As per `arch/arm64/include/uapi/asm/setup.h`.
