target/mips: Move sysemu specific files under sysemu/ subfolder

Move sysemu-specific files under the new sysemu/ subfolder
and adapt the Meson machinery.
Update the KVM MIPS entry in MAINTAINERS.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210428170410.479308-17-f4bug@amsat.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 4c05ff8..8e4e329 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -404,7 +404,8 @@
 MIPS KVM CPUs
 M: Huacai Chen <chenhuacai@kernel.org>
 S: Odd Fixes
-F: target/mips/kvm.c
+F: target/mips/kvm*
+F: target/mips/sysemu/
 
 PPC KVM CPUs
 M: David Gibson <david@gibson.dropbear.id.au>