asm: Remove Serial debug statements

This approch doesn't scale to our other ASM code and it clutters the output.

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

src/asm/ram64.s

@@ -3,11 +3,6 @@
 .code64
 
 ram64_start:
-    # Indicate (via serial) that we are in long/64-bit mode
-    movw $0x3f8, %dx
-    movb $'L', %al
-    outb %al, %dx
-
     # Setup the stack (at the end of our RAM region)
     movq $ram_max, %rsp