pnor_partition_table: Fix printf() format specifier for size_t

On x86_64 we receive the following warning from GCC:

    In file included from pnor_partition_table.cpp:2:0:
    pnor_partition_table.cpp: In member function ‘const pnor_partition& openpower::virtual_pnor::partition::Table::partition(size_t) const’:
    common.h:37:61: error: format ‘%x’ expects argument of type ‘unsigned int’, but argument 3 has type ‘size_t {aka long unsigned int}’ [-Werror=format=]
     #define MSG_ERR(f_, ...) mbox_log(LOG_ERR, f_, ##__VA_ARGS__)
                                                                 ^
    pnor_partition_table.cpp:218:5: note: in expansion of macro ‘MSG_ERR’
         MSG_ERR("Partition corresponding to offset %x not found", offset);
         ^~~~~~~

The type of %x may not match the size of the type on the host system. Use %zu
to avoid a compiler warning.

Change-Id: I79b0a33af6fc4e0c06c60457e89d0c4125d1e39d
Tested: Changed the format specifier and recompiled, observed no warnings
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/pnor_partition_table.cpp b/pnor_partition_table.cpp
index bb9e05d..b42907c 100644
--- a/pnor_partition_table.cpp
+++ b/pnor_partition_table.cpp
@@ -233,7 +233,7 @@
         }
     }
 
-    MSG_ERR("Partition corresponding to offset %x not found", offset);
+    MSG_ERR("Partition corresponding to offset %zu not found", offset);
     elog<InternalFailure>();
 
     static pnor_partition p{};