docs/system/target-sparc: Improve the Sparc documentation

Add some words about how to enable or disable boolean features,
and remove the note about a Linux kernel being available on the
QEMU website (they have been removed long ago already), and the
note about NetBSD and OpenBSD still having issues (they should
work fine nowadays).

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/2141
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240419084812.504779-4-thuth@redhat.com>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

docs/system/target-sparc.rst

@@ -27,6 +27,11 @@ architecture machines:
 The emulation is somewhat complete. SMP up to 16 CPUs is supported, but
 Linux limits the number of usable CPUs to 4.
 
+The list of available CPUs can be viewed by starting QEMU with ``-cpu help``.
+Optional boolean features can be added with a "+" in front of the feature name,
+or disabled with a "-" in front of the name, for example
+``-cpu TI-SuperSparc-II,+float128``.
+
 QEMU emulates the following sun4m peripherals:
 
 -  IOMMU
@@ -55,8 +60,5 @@ OpenBIOS is a free (GPL v2) portable firmware implementation. The goal
 is to implement a 100% IEEE 1275-1994 (referred to as Open Firmware)
 compliant firmware.
 
-A sample Linux 2.6 series kernel and ram disk image are available on the
-QEMU web site. There are still issues with NetBSD and OpenBSD, but most
-kernel versions work. Please note that currently older Solaris kernels
-don't work probably due to interface issues between OpenBIOS and
-Solaris.
+Please note that currently older Solaris kernels don't work; this is probably
+due to interface issues between OpenBIOS and Solaris.