stm32mp: dram_init: Fix AARCH64 compilation warnings

When building with AARCH64 defconfig, we got warnings for debug
message
- format '%x' expects argument of type 'unsigned int',
   but argument 3 has type 'size_t' {aka 'long unsigned int'}).
- format '%lx' expects argument of type 'long unsigned int',
  but argument 2 has type 'phys_addr_t' {aka 'long long unsigned
  int'}

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>