Inline the mmio accessor functions

Making the simple mmio_read_*() and mmio_write_*() functions inline
saves 360 bytes of code in FVP release build.

Fixes ARM-software/tf-issues#210

Change-Id: I65134f9069f3b2d8821d882daaa5fdfe16355e2f
Remove current CPU mpidr from PSCI common code

Many of the interfaces internal to PSCI pass the current CPU
MPIDR_EL1 value from function to function. This is not required,
and with inline access to the system registers is less efficient
than requiring the code to read that register whenever required.

This patch remove the mpidr parameter from the affected interfaces
and reduces code in FVP BL3-1 size by 160 bytes.

Change-Id: I16120a7c6944de37232016d7e109976540775602
Merge pull request #153 from athoelke/at/remove-psci-mpidr

Remove current CPU mpidr from PSCI common code
Merge pull request #154 from athoelke/at/inline-mmio

Inline the mmio accessor functions