Change in coreboot[master]: soc/intel/common/../car: Calculate SF Mask#1 based on MSR 0xc87

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Furquan Shaikh, Subrata Banik, Nick Vaccaro, EricR Lai.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/51374 )

Change subject: soc/intel/common/../car: Calculate SF Mask#1 based on MSR 0xc87
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Patch Set 8:

(2 comments)

File src/soc/intel/common/block/cpu/car/cache_as_ram.S:

https://review.coreboot.org/c/coreboot/+/51374/comment/8e925e5b_61b3c2e1 
PS8, Line 527:  2. Set SF_MASK_1 = ((1 << SFWayCnt) - 1) - ((1 << data_ways) - 1)
This can be simplified further to remove 1 subtraction:
`((1 << (SFWayCnt - data_ways)) - 1) << data_ways)`

It's the same number of shifts, but 1 fewer subtraction, which IMO it's almost always good to reduce instruction count in CAR, see below for a sequence that should work; I've also worked it to remove the need to save `ebx`

https://review.coreboot.org/c/coreboot/+/51374/comment/83bee73e_8c4265a6 
PS8, Line 532: mov	%al, %cl
             : 	mov	$0x01, %eax
             : 	shl	%cl, %eax
             : 	subl	$0x01, %eax /* contains ((1 << SFWayCnt) - 1) */
             : 	mov	%bl, %cl
             : 	mov	$0x01, %ebx
             : 	shl	%cl, %ebx
             : 	subl	$0x01, %ebx /* contains ((1 << data_ways) - 1) */
             : 	sub	%ebx, %eax /* contains SF mask */
`edx` is also free at this point, so I think that could be used instead of backing of `ebx` and using it, combined with the above, does this work? I think this saves something like 4 instructions, including the restore on 549
```
sequence:
ebx	== non-eviction mask
ecx	== number of ways
    /* save number of ways to edi because rdmsr has to use ecx */
    mov	%ecx, %edi       /* edi == data_ways */
    mov	$IA32_SF_QOS_INFO, %ecx /* ecx == IA32_SF_QOS_INFO */
    rdmsr
    and	$0x3f, %eax      /* eax == SFWayCnt */
    mov	%ecx, %edx       /* ecx == SFWayCnt */
    subl	%ecx, %edi       /* ecx == SFWayCnt - data_ways */
    movl	$0x01, %eax      /* eax == 1 */
    shl	$cl, %eax        /* eax == 1 << (SFWayCnt - data_ways) */
    subl	$0x01, %eax      /* eax == (1 << (SFWayCnt - data_ways)) - 1) */
    mov 	%edi, %ecx       /* ecx == data_ways */
    shl	%cl, %eax        /* eax == ((1 << (SFWayCnt - data_ways)) - 1)) << data_ways */
```

and then the mask value we want is in eax ready to be used with `wrmsr`
WDYT?