Remove tentative purpose for reserved misa.B and misa.J bits

This change has no normative effect.

What were formerly informally referred to as the B and J extensions
are instead going to become multiple smaller and disjoint extensions.
Since it appears unlikely that B and J will ultimately have any
meaning, simply mark these misa bits as "reserved", rather than
"tentatively reserved for X".

Author: aswaterman

src/machine.tex

@@ -116,15 +116,15 @@ \subsection{Machine ISA Register {\tt misa}}
 Bit & Character  & Description \\
 \hline
   0 & A & Atomic extension \\
-  1 & B & {\em Tentatively reserved for Bit-Manipulation extension} \\
+  1 & B & {\em Reserved} \\
   2 & C & Compressed extension \\
   3 & D & Double-precision floating-point extension \\
   4 & E & RV32E base ISA \\
   5 & F & Single-precision floating-point extension \\
   6 & G & {\em Reserved} \\
   7 & H & Hypervisor extension \\
   8 & I & RV32I/64I/128I base ISA \\
-  9 & J & {\em Tentatively reserved for Dynamically Translated Languages extension} \\
+  9 & J & {\em Reserved} \\
  10 & K & {\em Reserved} \\
  11 & L & {\em Reserved} \\
  12 & M & Integer Multiply/Divide extension \\