arm64: docs: cpu-feature-registers: Document ID_AA64PFR1_EL1

Commit d71be2b6 ("arm64: cpufeature: Detect SSBS and advertise
to userspace") exposes ID_AA64PFR1_EL1 to userspace, but didn't
update the documentation to match.

Add it.
Acked-by: NWill Deacon <will@kernel.org>
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Signed-off-by: NMark Brown <broonie@kernel.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Documentation/arm64/cpu-feature-registers.rst

@@ -168,8 +168,15 @@ infrastructure:
      +------------------------------+---------+---------+
 
 
-  3) MIDR_EL1 - Main ID Register
+  3) ID_AA64PFR1_EL1 - Processor Feature Register 1
+     +------------------------------+---------+---------+
+     | Name                         |  bits   | visible |
+     +------------------------------+---------+---------+
+     | SSBS                         | [7-4]   |    y    |
+     +------------------------------+---------+---------+
+
 
+  4) MIDR_EL1 - Main ID Register
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |
      +------------------------------+---------+---------+
@@ -188,7 +195,7 @@ infrastructure:
    as available on the CPU where it is fetched and is not a system
    wide safe value.
 
-  4) ID_AA64ISAR1_EL1 - Instruction set attribute register 1
+  5) ID_AA64ISAR1_EL1 - Instruction set attribute register 1
 
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |
@@ -210,7 +217,7 @@ infrastructure:
      | DPB                          | [3-0]   |    y    |
      +------------------------------+---------+---------+
 
-  5) ID_AA64MMFR2_EL1 - Memory model feature register 2
+  6) ID_AA64MMFR2_EL1 - Memory model feature register 2
 
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |
@@ -218,7 +225,7 @@ infrastructure:
      | AT                           | [35-32] |    y    |
      +------------------------------+---------+---------+
 
-  6) ID_AA64ZFR0_EL1 - SVE feature ID register 0
+  7) ID_AA64ZFR0_EL1 - SVE feature ID register 0
 
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |