lib: Fix SYS_TIMER_COUNTS_DOWN description in Kconfig

The SYS_TIMER_COUNTS_DOWN description contains a typo,
s@rathe@&r@ , fix it.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/lib/Kconfig b/lib/Kconfig
index 4278b24..202a34a 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -16,7 +16,7 @@
 	  Sets the number of entries in the virtual-physical mapping table.
 
 config SYS_TIMER_COUNTS_DOWN
-	bool "System timer counts down rathe than up"
+	bool "System timer counts down rather than up"
 
 config PHYSMEM
 	bool "Access to physical memory region (> 4G)"