Revert "boot/efi: fall back to legacy UART if EFI protocol is not available"

This reverts commit 50913d9a6f.

Reason for revert: this change broke the UEFI loader, see ticket #17880

Change-Id: Iefc0e53a09ddff94d7f0f2d4016af9119425af78
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5576
Reviewed-by: waddlesplash <[email protected]>

src/system/boot/platform/efi/serial.cpp

@@ -39,9 +39,7 @@ enum serial_register_offsets {
 	SERIAL_MODEM_STATUS			= 6,
 };
 
-#if defined(__i386__) || defined(__x86_64__)
 static uint16 sSerialBasePort = 0x3f8;
-#endif
 
 
 DebugUART* gUART = NULL;
@@ -127,7 +125,6 @@ serial_init(void)
 
 	if (status != EFI_SUCCESS || sSerial == NULL) {
 		sSerial = NULL;
-		sSerialUsesEFI = false;
 		return;
 	}