target/alpha: Remove `NB_MMU_MODES` define

Signed-off-by: Anton Johansson <anjo@rev.ng>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230306175230.7110-3-anjo@rev.ng>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/alpha/cpu-param.h

@@ -15,6 +15,4 @@
 #define TARGET_PHYS_ADDR_SPACE_BITS  44
 #define TARGET_VIRT_ADDR_SPACE_BITS  (30 + TARGET_PAGE_BITS)
 
-#define NB_MMU_MODES 3
-
 #endif