Kconfig: memtest: update number of test patterns up to 17

Additional test patterns for memtest were introduced since commit
63823126c221 ("x86: memtest: add additional (regular) test patterns"),
but looks like Kconfig was not updated that time.

Update Kconfig entry with the actual number of maximum test patterns.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.debug

@@ -1754,7 +1754,7 @@ config MEMTEST
 	        memtest=0, mean disabled; -- default
 	        memtest=1, mean do 1 test pattern;
 	        ...
-	        memtest=4, mean do 4 test patterns.
+	        memtest=17, mean do 17 test patterns.
 	  If you are unsure how to answer this question, answer N.
 
 source "samples/Kconfig"