Add driver manager's setup routine

The setup_drivers routine existed locally for some time now, so now
it also exists in the repository. It has gone through two iterations:

1. The drivers are all listed in a null-terminated array of function
   pointers to initialization functions (this didn't work and the time
   for debugging just wasn't there).

2. All drivers (currently, only the PCI driver, because that's the
   only one that exists) are initialized after each other; their
   initialization functions are called manually.

It might be possible that the bug from the first iteration was due to
the memory space being offset by 128 or 256 bytes; it might be useful
to use that concept again because then, it will be easier to add new
drivers. That's not of high importance now, though.

i386/loader/src-asm/drivers/manager.asm

@@ -0,0 +1,47 @@
+
+; Start with the driver data at 1 MiB, continue for 2 MiB
+DRIVER_MEMORY_AREA      equ 0x100000
+DRIVER_SLOT_SIZE        equ 65536
+DRIVER_SLOT_COUNT       equ 32
+
+; Functions of all drivers which get initialized (in the order of
+; initialization); the last entry must be a zero, but at 32 entries,
+; the end is forced by the main initialization function.
+driver_init_functions:
+    dd          initialize_pci_driver
+    ; Ending Entry
+    dd          0
+
+; [Furthest from EBP]
+;   -- No Arguments --
+; [Nearest to EBP]
+setup_drivers:
+    push        dword                   esi
+    sub         esp,                    64
+    mov         esi,                    esp
+
+    mov         [esi + (64 - 4)],       eax
+    mov         [esi + (64 - 8)],       ebx
+    mov         [esi + (64 - 12)],      ecx
+    mov         [esi + (64 - 16)],      edx
+    mov         [esi + (64 - 20)],      edi
+
+    push        ebp
+    mov         ebp,                    esp
+    push        dword DRIVER_MEMORY_AREA
+    call        initialize_pci_driver
+    mov         esp,                    ebp
+    pop         ebp
+
+.epilog:
+    mov         eax,                    [esi + (64 - 4)]
+    mov         ebx,                    [esi + (64 - 8)]
+    mov         ecx,                    [esi + (64 - 12)]
+    mov         edx,                    [esi + (64 - 16)]
+    mov         edi,                    [esi + (64 - 20)]
+
+    add         esp,                    64
+    pop         dword esi
+    ret
+
+%include "drivers/pci/driver.asm"