target/sparc: Make sparc_cpu_tlb_fill sysemu only

The fallback code in cpu_loop_exit_sigsegv is sufficient
for sparc linux-user.

This makes all of the code in mmu_helper.c sysemu only, so remove
the ifdefs and move the file to sparc_softmmu_ss.  Remove the code
from cpu_loop that handled TT_DFAULT and TT_TFAULT.

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

target/sparc/meson.build

@@ -6,7 +6,6 @@ sparc_ss.add(files(
   'gdbstub.c',
   'helper.c',
   'ldst_helper.c',
-  'mmu_helper.c',
   'translate.c',
   'win_helper.c',
 ))
@@ -16,6 +15,7 @@ sparc_ss.add(when: 'TARGET_SPARC64', if_true: files('int64_helper.c', 'vis_helpe
 sparc_softmmu_ss = ss.source_set()
 sparc_softmmu_ss.add(files(
   'machine.c',
+  'mmu_helper.c',
   'monitor.c',
 ))