powerpc/fadump: reset dump area size if fadump memory reserve fails

In case fadump_reserve_mem() fails to reserve memory, the
reserve_dump_area_size variable will retain the reserve area size. This
will lead to /sys/kernel/fadump/mem_reserved node displaying an incorrect
memory reserved by fadump.

To fix this problem, reserve dump area size variable is set to 0 if fadump
failed to reserve memory.

Fixes: 8255da95 ("powerpc/fadump: release all the memory above boot memory size")
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230704050715.203581-1-sourabhjain@linux.ibm.com

arch/powerpc/kernel/fadump.c

@@ -654,6 +654,7 @@ int __init fadump_reserve_mem(void)
 	return ret;
 error_out:
 	fw_dump.fadump_enabled = 0;
+	fw_dump.reserve_dump_area_size = 0;
 	return 0;
 }