hw/sparc*: Move cpu_check_irqs() to target/sparc/

hw/sparc*: Move cpu_check_irqs() to target/sparc/

Since cpu_check_irqs() doesn't reference to anything outside
of CPUSPARCState, it better belongs to the architectural code
in target/, rather than the hardware specific code in hw/.

Note: while we moved the trace events, we don't rename them.

Remark: this allows us to build the leon3 machine stand alone,
fixing this link failure (because cpu_check_irqs is defined in
hw/sparc/sun4m.c which is only built when CONFIG_SUN4M is selected):

  /usr/bin/ld: target_sparc_win_helper.c.o: in function `cpu_put_psr':
  target/sparc/win_helper.c:91: undefined reference to `cpu_check_irqs'

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210428141655.387430-5-f4bug@amsat.org>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>