arm64: Documentation: Fix broken table in generated HTML

cpu-feature-registers.rst is missing a new line before a couple
of tables listing the visible fields, causing broken tables in
the HTML documentation generated by "make htmldocs". Fix this
by adding the missing new line.
Reported-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20200707143152.154541-1-suzuki.poulose@arm.comSigned-off-by: NWill Deacon <will@kernel.org>

Documentation/arm64/cpu-feature-registers.rst

@@ -171,6 +171,7 @@ infrastructure:
 
 
   3) ID_AA64PFR1_EL1 - Processor Feature Register 1
+
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |
      +------------------------------+---------+---------+
@@ -181,6 +182,7 @@ infrastructure:
 
 
   4) MIDR_EL1 - Main ID Register
+
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |
      +------------------------------+---------+---------+