docs: Downgrade arm64 & riscv from titles to comment

Remove the title string ("====") from under arm64 & riscv and move them
to a commment under the perf_user_access sysctl. They are explanations,
*not* sysctls themselves

This effectively removes these two strings from appearing as not
implemented when the check-sysctl-docs script is run

Signed-off-by: Joel Granados <joel.granados@kernel.org>

Author: Joelgranados

Documentation/admin-guide/sysctl/kernel.rst

@@ -1014,30 +1014,26 @@ perf_user_access (arm64 and riscv only)
 
 Controls user space access for reading perf event counters.
 
-arm64
-=====
-
-The default value is 0 (access disabled).
+* for arm64
+  The default value is 0 (access disabled).
 
-When set to 1, user space can read performance monitor counter registers
-directly.
+  When set to 1, user space can read performance monitor counter registers
+  directly.
 
-See Documentation/arch/arm64/perf.rst for more information.
-
-riscv
-=====
+  See Documentation/arch/arm64/perf.rst for more information.
 
-When set to 0, user space access is disabled.
+* for riscv
+  When set to 0, user space access is disabled.
 
-The default value is 1, user space can read performance monitor counter
-registers through perf, any direct access without perf intervention will trigger
-an illegal instruction.
+  The default value is 1, user space can read performance monitor counter
+  registers through perf, any direct access without perf intervention will trigger
+  an illegal instruction.
 
-When set to 2, which enables legacy mode (user space has direct access to cycle
-and insret CSRs only). Note that this legacy value is deprecated and will be
-removed once all user space applications are fixed.
+  When set to 2, which enables legacy mode (user space has direct access to cycle
+  and insret CSRs only). Note that this legacy value is deprecated and will be
+  removed once all user space applications are fixed.
 
-Note that the time CSR is always directly accessible to all modes.
+  Note that the time CSR is always directly accessible to all modes.
 
 pid_max
 =======