powerpc/44x: fix spelling mistake in Kconfig "varients" -> "variants"

There is a spelling mistake in the Kconfig help text. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201216113608.11812-1-colin.king@canonical.com

arch/powerpc/platforms/44x/Kconfig

@@ -5,7 +5,7 @@ config PPC_47x
 	select MPIC
 	help
 	  This option enables support for the 47x family of processors and is
-	  not currently compatible with other 44x or 46x varients
+	  not currently compatible with other 44x or 46x variants
 
 config BAMBOO
 	bool "Bamboo"