powerpc/ep8248e: Use %pa to format resource_size_t

powerpc/ep8248e: Use %pa to format resource_size_t

The correct format string for resource_size_t is %pa which
acts on the address of the variable to be formatted [1].

[1] https://elixir.bootlin.com/linux/v6.11.3/source/Documentation/core-api/printk-formats.rst#L229

Introduced by commit 9d9326d3bc0e ("phy: Change mii_bus id field to a string")

Flagged by gcc-14 as:
arch/powerpc/platforms/82xx/ep8248e.c: In function 'ep8248e_mdio_probe':
arch/powerpc/platforms/82xx/ep8248e.c:131:46: warning: format '%x' expects argument of type 'unsigned int', but argument 4 has type 'resource_size_t' {aka 'long long unsigned int'} [-Wformat=]
  131 |         snprintf(bus->id, MII_BUS_ID_SIZE, "%x", res.start);
      |                                             ~^   ~~~~~~~~~
      |                                              |      |
      |                                              |      resource_size_t {aka long long unsigned int}
      |                                              unsigned int
      |                                             %llx

No functional change intended.
Compile tested only.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/netdev/711d7f6d-b785-7560-f4dc-c6aad2cce99@linux-m68k.org/
Signed-off-by: Simon Horman <horms@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241014-ep8248e-pa-fmt-v1-1-009ea0dcc18f@kernel.org