mxgrub: Change crashkernel size to 512MB

Systems like "kreios" panic during initialization of the panic kernel
with out of memory. Double the memory size for the panic kernel.

This is an experiment, because for systems with <8GB we surly don't want
to reserve 512 MB.

mxgrub/mxgrub

@@ -239,7 +239,7 @@ sub scan_mariux {
 	}
 }
 
-our $KERNEL_PARAMETER="ro crashkernel=256M console=ttyS0,115200n8 console=ttyS1,115200n8 console=tty0 init=/bin/systemd audit=0";
+our $KERNEL_PARAMETER="ro crashkernel=512M console=ttyS0,115200n8 console=ttyS1,115200n8 console=tty0 init=/bin/systemd audit=0";
 
 sub update_grub_cfg {
 	my $kernellist='';