Factor out common parts of flen files

Similar to what was done to XLEN already, place the the types/variables that are derived from FLEN into a separate file that is always included and only leave the value of FLEN itself in the F/D specific files.

Makefile

@@ -17,6 +17,7 @@ endif
 
 SAIL_XLEN += riscv_xlen.sail
 SAIL_FLEN := riscv_flen_D.sail
+SAIL_FLEN += riscv_flen.sail
 SAIL_VLEN := riscv_vlen.sail
 
 # Instruction sources, depending on target

model/riscv_flen.sail

@@ -0,0 +1,14 @@
+/*=======================================================================================*/
+/*  This Sail RISC-V architecture model, comprising all files and                        */
+/*  directories except where otherwise noted is subject the BSD                          */
+/*  two-clause license in the LICENSE file.                                              */
+/*                                                                                       */
+/*  SPDX-License-Identifier: BSD-2-Clause                                                */
+/*=======================================================================================*/
+
+type flenbits = bits(flen)
+
+// Variable versions of the above types. Variables and types
+// are disjoint in Sail so they are allowed to have the same name.
+// This saves typing `sizeof()` everywhere.
+let flen = sizeof(flen)

model/riscv_flen_D.sail

@@ -8,10 +8,4 @@
 
 /* Define the FLEN value for the 'D' extension. */
 
-type flen       : Int = 64
-type flenbits         = bits(flen)
-
-// Variable versions of the above types. Variables and types
-// are disjoint in Sail so they are allowed to have the same name.
-// This saves typing `sizeof()` everywhere.
-let flen = sizeof(flen)
+type flen : Int = 64

model/riscv_flen_F.sail

@@ -8,10 +8,4 @@
 
 /* Define the FLEN value for the 'F' extension. */
 
-type flen       : Int = 32
-type flenbits         = bits(flen)
-
-// Variable versions of the above types. Variables and types
-// are disjoint in Sail so they are allowed to have the same name.
-// This saves typing `sizeof()` everywhere.
-let flen = sizeof(flen)
+type flen : Int = 32