x86/bugs: Correct RSB terminology in Kconfig

RSB stands for "Return Stack Buffer" in industry literature[1]. Update
the kernel Kconfig to use this standard term instead of the current
"Return-Speculation-Buffer".

This change aligns kernel documentation with widely accepted terminology.

The line length reduction triggers text reformatting, but no functional
text is altered.

[1] https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/advisory-guidance/return-stack-buffer-underflow.html

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20240913122754.249306-1-leitao%40debian.org

arch/x86/Kconfig

@@ -2551,15 +2551,14 @@ config MITIGATION_CALL_DEPTH_TRACKING
 	default y
 	help
 	  Compile the kernel with call depth tracking to mitigate the Intel
-	  SKL Return-Speculation-Buffer (RSB) underflow issue. The
-	  mitigation is off by default and needs to be enabled on the
-	  kernel command line via the retbleed=stuff option. For
-	  non-affected systems the overhead of this option is marginal as
-	  the call depth tracking is using run-time generated call thunks
-	  in a compiler generated padding area and call patching. This
-	  increases text size by ~5%. For non affected systems this space
-	  is unused. On affected SKL systems this results in a significant
-	  performance gain over the IBRS mitigation.
+	  SKL Return-Stack-Buffer (RSB) underflow issue. The mitigation is off
+	  by default and needs to be enabled on the kernel command line via the
+	  retbleed=stuff option. For non-affected systems the overhead of this
+	  option is marginal as the call depth tracking is using run-time
+	  generated call thunks in a compiler generated padding area and call
+	  patching. This increases text size by ~5%. For non affected systems
+	  this space is unused. On affected SKL systems this results in a
+	  significant performance gain over the IBRS mitigation.
 
 config CALL_THUNKS_DEBUG
 	bool "Enable call thunks and call depth tracking debugging"