sys: parse drive number and load BPB

com/hello.asm

@@ -1,15 +0,0 @@
-; COM program displaying hello world string
-; This is primarily for testing purposes
-	org 0x0100
-
-main:	mov si, string
-	mov ah, 0x0e
-	xor bx, bx
-.loop:	lodsb
-	test al, al
-	jz .end
-	int 0x10
-	jmp .loop
-.end:	ret
-
-string:	db "Hello world!", 0x0A, 0x0D, 0