powerpc/xmon: remove unused ppc_parse_cpu() declaration

ppc_parse_cpu() has been removed since
commit 5b102782 ("powerpc/xmon: Enable disassembly
files (compilation changes)"), so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220913075029.682327-2-cuigaosheng1@huawei.com

arch/powerpc/xmon/ppc.h

@@ -435,8 +435,6 @@ struct powerpc_macro
 extern const struct powerpc_macro powerpc_macros[];
 extern const int powerpc_num_macros;
 
-extern ppc_cpu_t ppc_parse_cpu (ppc_cpu_t, ppc_cpu_t *, const char *);
-
 static inline long
 ppc_optional_operand_value (const struct powerpc_operand *operand)
 {