Add PLAT_xxx_ADDR_SPACE_SIZE definitions

Added the definitions `PLAT_PHY_ADDR_SPACE_SIZE` and
`PLAT_VIRT_ADDR_SPACE_SIZE` which specify respectively the physical
and virtual address space size a platform can use.

`ADDR_SPACE_SIZE` is now deprecated. To maintain compatibility, if any
of the previous defines aren't present, the value of `ADDR_SPACE_SIZE`
will be used instead.

For AArch64, register ID_AA64MMFR0_EL1 is checked to calculate the
max PA supported by the hardware and to verify that the previously
mentioned definition is valid. For AArch32, a 40 bit physical
address space is considered.

Added asserts to check for overflows.

Porting guide updated.

Change-Id: Ie8ce1da5967993f0c94dbd4eb9841fc03d5ef8d6
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index a013809..aa26203 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -196,6 +196,7 @@
  ******************************************************************************/
 DEFINE_SYSREG_READ_FUNC(midr_el1)
 DEFINE_SYSREG_READ_FUNC(mpidr_el1)
+DEFINE_SYSREG_READ_FUNC(id_aa64mmfr0_el1)
 
 DEFINE_SYSREG_RW_FUNCS(scr_el3)
 DEFINE_SYSREG_RW_FUNCS(hcr_el2)