RISC-V: Use "@minus{}2 GB" instead of "-2 GB" in invoke.texi

gcc/ChangeLog

2017-11-01  Palmer Dabbelt  <palmer@dabbelt.com>

	* doc/invoke.texi (RISC-V Options): Use "@minus{}2 GB", not "-2 GB".

From-SVN: r254331

gcc/ChangeLog

+2017-11-01  Palmer Dabbelt  <palmer@dabbelt.com>
+
+	* doc/invoke.texi (RISC-V Options): Use "@minus{}2 GB", not "-2 GB".
+
 2017-11-01  Jeff Law  <law@redhat.com>
 
 	* tree-ssa-ccp.c (ccp_folder): New class derived from

gcc/doc/invoke.texi

@@ -21769,8 +21769,8 @@ Do not generate unaligned memory accesses.
 @opindex mcmodel=medlow
 Generate code for the medium-low code model. The program and its statically
 defined symbols must lie within a single 2 GiB address range and must lie
-between absolute addresses -2 GiB and +2 GiB. Programs can be statically or
-dynamically linked. This is the default code model.
+between absolute addresses @minus{}2 GiB and +2 GiB. Programs can be
+statically or dynamically linked. This is the default code model.
 
 @item -mcmodel=medany
 @opindex mcmodel=medany