mainboard: Drop optional and empty ACPI \_BFS methods

The ACPI specification, version 2.0 says:

    _BFS is an optional control method.

So, remove them. They have been copy-pasted around quite a bit, and do
not do anything useful. Plus, it's deprecated in later ACPI versions.

Change-Id: I9ef21f231dd6051d410ac3a0fe554908409c2fa7
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43443
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/biostar/a68n_5200/acpi/sleep.asl

@@ -36,22 +36,6 @@ Method(_PTS, 1) {
 	\_SB.APTS(Arg0)
 } /* End Method(\_PTS) */
 
-/*
-*	\_BFS OEM Back From Sleep method
-*
-*	Entry:
-*		Arg0=The value of the sleeping state S1=1, S2=2
-*
-*	Exit:
-*		-none-
-*/
-Method(\_BFS, 1) {
-	/* DBGO("\\_BFS\n") */
-	/* DBGO("From S") */
-	/* DBGO(Arg0) */
-	/* DBGO(" to S0\n") */
-}
-
 /*
 *  \_WAK System Wake method
 *

src/mainboard/biostar/am1ml/acpi/sleep.asl

@@ -36,22 +36,6 @@ Method(_PTS, 1) {
 	\_SB.APTS(Arg0)
 } /* End Method(\_PTS) */
 
-/*
-*	\_BFS OEM Back From Sleep method
-*
-*	Entry:
-*		Arg0=The value of the sleeping state S1=1, S2=2
-*
-*	Exit:
-*		-none-
-*/
-Method(\_BFS, 1) {
-	/* DBGO("\\_BFS\n") */
-	/* DBGO("From S") */
-	/* DBGO(Arg0) */
-	/* DBGO(" to S0\n") */
-}
-
 /*
 *  \_WAK System Wake method
 *