mb/asrock/b75pro3-m: Remove cpu_fan_tach_src from CMOS layout

Commit 65c456227e (mb/asrock/b75pro3-m: Add CMOS layout/defaults and
vbt.bin) introduced CMOS settings for selecting CPU_FAN{1,2}, but this
code was never implemented.  Remove the fake setting for it.

Signed-off-by: Fabian Groffen <grobian@gentoo.org>
Change-Id: Ic2f4aa42f9cfd77defc2a11e16643690356bc26b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73939
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kevin Keijzer <kevin@quietlife.nl>
Reviewed-by: Felix Singer <felixsinger@posteo.net>

src/mainboard/asrock/b75pro3-m/cmos.default

@@ -4,4 +4,3 @@ nmi=Disable
 power_on_after_fail=Disable
 sata_mode=AHCI
 gfx_uma_size=64M
-cpu_fan_tach_src=CPU_FAN1

src/mainboard/asrock/b75pro3-m/cmos.layout

@@ -24,9 +24,6 @@ entries
 # coreboot config options: northbridge
 416	5	e	6	gfx_uma_size
 
-# coreboot config options: mainboard-specific
-421	2	e	7	cpu_fan_tach_src
-
 # coreboot config options: check sums
 984	16	h	0	check_sum
 
@@ -83,13 +80,6 @@ enumerations
 6	15	512M
 6	16	1024M
 
-# cpu_fan_header (select which header provides the tachometer
-# signal to the Super I/O on its CPUFANIN input)
-7	0	None
-7	1	CPU_FAN1
-7	2	CPU_FAN2
-7	3	Both
-
 # -----------------------------------------------------------------
 checksums