hw/intc/arm_gic: Rename 'first_cpu' argument

hw/intc/arm_gic: Rename 'first_cpu' argument

"hw/core/cpu.h" defines 'first_cpu' as QTAILQ_FIRST_RCU(&cpus).

arm_gic_common_reset_irq_state() calls its second argument
'first_cpu', producing a build failure when "hw/core/cpu.h"
is included:

  hw/intc/arm_gic_common.c:238:68: warning: omitting the parameter name in a function definition is a C2x extension [-Wc2x-extensions]
    static inline void arm_gic_common_reset_irq_state(GICState *s, int first_cpu,
                                                                       ^
  include/hw/core/cpu.h:451:26: note: expanded from macro 'first_cpu'
    #define first_cpu        QTAILQ_FIRST_RCU(&cpus)
                             ^

KISS, rename the function argument.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230405160454.97436-5-philmd@linaro.org>