Fix text display for rows other than the first

Because the calculation of the byte offset within the framebuffer was
wrong, the framebuffer could only be written to on the first line.
That is now fixed.

i386/loader/src-asm/utility/display.asm

@@ -33,20 +33,21 @@ write_hexadecimal_string:
     ; character uses 2 bytes and there are 3 characters per byte
     ; written; the upper nibble, the lower nibble and the padding.
 
-    ; Multiply the row with 80, the number of cells per row
+    ; Multiply the row with 160, the number of bytes per row
     mov eax, [ebp - 16]
-    mov edx, 80
+    mov edx, 160
     mul edx
+    mov [esi + 4], eax
 
-    ; Add the offset within the row ontop
-    add eax, [ebp - 12]
+    ; Get the byte offset within the row
+    mov eax, [ebp - 12]
     add eax, ecx
-
-    ; Multiply with 2 to get the byte offset
-    ; from the character index
     mov edx, 6
     mul edx
 
+    ; Add the start offset of the line
+    add eax, [esi + 4]
+
     ; Point into the framebuffer
     add eax, FRAMEBUFFER_ADDRESS