acpi/Kconfig: improve description of ACPI_CPU_STRING config option

ACPI_CPU_STRING specifies the format string for the scope of the
processor devices in the generated ACPI code. Also point out that the
resulting string will be truncated to at most 15 chars to fit into the
16 byte buffer used in two functions in acpigen.c.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I1fb1db8adeecd783c835a500d28a13b823cda155
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72451
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
diff --git a/src/acpi/Kconfig b/src/acpi/Kconfig
index 816f9fb..ec7fcc4 100644
--- a/src/acpi/Kconfig
+++ b/src/acpi/Kconfig
@@ -11,9 +11,10 @@
 	default "\\_SB.CP%02X"
 	depends on HAVE_ACPI_TABLES
 	help
-	  Sets the ACPI name string in the processor scope as written by
-	  the acpigen function. Default is \_SB.CPxx. Note that you need
-	  the \ escape character in the string.
+	  Specifies the ACPI name format string used by the acpigen
+	  function to generate the processor scope. Default is \_SB.CPxx.
+	  Note that you need to escape the '\' character in the string.
+	  The resulting string will be truncated to at most 15 chars.
 
 config ACPI_HAVE_PCAT_8259
 	def_bool y if !ACPI_NO_PCAT_8259