MOCK: RISC-V: Tests for 'Zce' implications

**NEVER COMMIT THIS.**

This commit is intended to be merged to the previous patch once 'Zcmp'
and 'Zcmt' extensions are ready.

It adds several tests related to 'Zce' implications.

bfd/ChangeLog:

	* elfxx-riscv.c: [MOCK] Uncomment mock lines to pass the test.

gas/ChangeLog:

	* testsuite/gas/riscv/march-imply-zce.d: New test.
	* testsuite/gas/riscv/march-imply-zce-f-32.d: Likewise.
	* testsuite/gas/riscv/march-imply-zce-f-64.d: Likewise.

bfd/elfxx-riscv.c

@@ -1350,10 +1350,9 @@ static struct riscv_supported_ext riscv_supported_std_z_ext[] =
   {"zcb",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
   {"zcf",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
   {"zcd",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
-  /* MOCK: uncomment those lines once ready.  */
-  // {"zce",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
-  // {"zcmp",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
-  // {"zcmt",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
+  {"zce",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
+  {"zcmp",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
+  {"zcmt",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
   {NULL, 0, 0, 0, 0}
 };
 

gas/testsuite/gas/riscv/march-imply-zce-f-32.d

@@ -0,0 +1,6 @@
+#as: -march=rv32if_zce -march-attr -misa-spec=20191213
+#readelf: -A
+#source: empty.s
+Attribute Section: riscv
+File Attributes
+  Tag_RISCV_arch: "rv32i2p1_f2p2_zicsr2p0_zca1p0_zcb1p0_zce1p0_zcf1p0_zcmp1p0_zcmt1p0"

gas/testsuite/gas/riscv/march-imply-zce-f-64.d

@@ -0,0 +1,6 @@
+#as: -march=rv64if_zce -march-attr -misa-spec=20191213
+#readelf: -A
+#source: empty.s
+Attribute Section: riscv
+File Attributes
+  Tag_RISCV_arch: "rv64i2p1_f2p2_zicsr2p0_zca1p0_zcb1p0_zce1p0_zcmp1p0_zcmt1p0"

gas/testsuite/gas/riscv/march-imply-zce.d

@@ -0,0 +1,6 @@
+#as: -march=rv32i_zce -march-attr -misa-spec=20191213
+#readelf: -A
+#source: empty.s
+Attribute Section: riscv
+File Attributes
+  Tag_RISCV_arch: "rv32i2p1_zca1p0_zcb1p0_zce1p0_zcmp1p0_zcmt1p0"