kvm: replace fprintf with error_report()/printf() in kvm_init()

kvm: replace fprintf with error_report()/printf() in kvm_init()

error_report() is more appropriate for error situations. Replace fprintf with
error_report() and error_printf() as appropriate. Some improvement in error
reporting also happens as a part of this change. For example:

From:
$ ./qemu-system-x86_64 --accel kvm
Could not access KVM kernel module: No such file or directory

To:
$ ./qemu-system-x86_64 --accel kvm
qemu-system-x86_64: --accel kvm: Could not access KVM kernel module: No such file or directory

CC: qemu-trivial@nongnu.org
CC: zhao1.liu@intel.com
CC: armbru@redhat.com
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Ani Sinha <anisinha@redhat.com>
Link: https://lore.kernel.org/r/20240828124539.62672-1-anisinha@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>