install.texi: Bump newlib version for nvptx + gcn

Before, newlib 3.2 was required for amdgcn and 3.1 for nvptx.
Now recommended is 4.3.0 which was just released on 2023-01-20.

While currently the old versions would work fine, upcoming GCC 
changes depend on a newer newlib. Thus, the minimal version is
bumped instead of just recommending the new version.

For GCN, the bump is in preparation for permitting non-threadlocal
stack variables and vectorized math functions - both scheduled for
GCC 13 and added to newlib in 4.3.0.

For nvptx, this includes an emulated clock (commit 6bb96d13a),
a calloc fix (5fca4e0f1) and changes to permit libgfortran to be
compiled with I/O support instead of only in minimal mode.
(Patch approved for GCC 13 but pending on a nvtpx patch.)

gcc/ChangeLog:

	* doc/install.texi (amdgcn, nvptx): Require newlib 4.3.0.

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index ccc8d15fd08..b1861a6a437 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -3855,7 +3855,7 @@ Instead of GNU Binutils, you will need to install LLVM 13.0.1, or later, and cop
 @file{bin/llvm-ar} to both @file{bin/amdgcn-amdhsa-ar} and
 @file{bin/amdgcn-amdhsa-ranlib}.
 
-Use Newlib (3.2.0, or newer).
+Use Newlib (4.3.0 or newer).
 
 To run the binaries, install the HSA Runtime from the
 @uref{https://rocm.github.io,,ROCm Platform}, and use
@@ -4672,7 +4672,7 @@ Instead of GNU binutils, you will need to install
 Tell GCC where to find it:
 @option{--with-build-time-tools=[install-nvptx-tools]/nvptx-none/bin}.
 
-You will need newlib 3.1.0 or later.  It can be
+You will need newlib 4.3.0 or later.  It can be
 automatically built together with GCC@.  For this, add a symbolic link
 to nvptx-newlib's @file{newlib} directory to the directory containing
 the GCC sources.