Replace all SCP FW (BL0, BL3-0) references

Replace all SCP FW (BL0, BL3-0) references

This patch replaces all references to the SCP Firmware (BL0, BL30,
BL3-0, bl30) with the image terminology detailed in the TF wiki
(https://github.com/ARM-software/arm-trusted-firmware/wiki):

    BL0          -->  SCP_BL1
    BL30, BL3-0  -->  SCP_BL2
    bl30         -->  scp_bl2

This change affects code, documentation, build system, tools and
platform ports that load SCP firmware. ARM plaforms have been
updated to the new porting API.

IMPORTANT: build option to specify the SCP FW image has changed:

    BL30 --> SCP_BL2

IMPORTANT: This patch breaks compatibility for platforms that use BL2
to load SCP firmware. Affected platforms must be updated as follows:

    BL30_IMAGE_ID --> SCP_BL2_IMAGE_ID
    BL30_BASE --> SCP_BL2_BASE
    bl2_plat_get_bl30_meminfo() --> bl2_plat_get_scp_bl2_meminfo()
    bl2_plat_handle_bl30() --> bl2_plat_handle_scp_bl2()

Change-Id: I24c4c1a4f0e4b9f17c9e4929da815c4069549e58