ARM: 8821/1: Correct meaning of SCU in HAVE_ARM_SCU help txt

According to the ARM Cortex-A5 and Cortex-A9 Technical Reference
Manuals, SCU stands for "Snoop Control Unit".
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>

arch/arm/Kconfig

@@ -1304,7 +1304,7 @@ config SCHED_SMT
 config HAVE_ARM_SCU
 	bool
 	help
-	  This option enables support for the ARM system coherency unit
+	  This option enables support for the ARM snoop control unit
 
 config HAVE_ARM_ARCH_TIMER
 	bool "Architected timer support"