build: clarify linker script generation

The following build system variables have been renamed:

- `LINKERFILE` -> `DEFAULT_LINKER_SCRIPT`
- `BL_LINKERFILE` -> `DEFAULT_LINKER_SCRIPT_SOURCE`
- `<IMAGE>_LINKERFILE` -> `<IMAGE>_DEFAULT_LINKER_SCRIPT_SOURCE`

These new names better reflect how each variable is used:

1. the default linker script is passed via `-dT` instead of `-T`
2. linker script source files are first preprocessed

Additionally, linker scripts are now placed in the build directory
relative to where they exist in the source directory. For example,
the `bl32/sp_min/sp_min.ld.S` would now preprocess to
`sp_min/sp_min.ld` instead of just `bl32.ld`

BREAKING-CHANGE: The `LINKERFILE`, `BL_LINKERFILE` and
 `<IMAGE_LINKERFILE>` build system variables have been renamed. See the
 commit message for more information.

Change-Id: If8cef65dcb8820e8993736702c8741e97a66e6cc
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/plat/marvell/armada/a8k/common/ble/ble.mk b/plat/marvell/armada/a8k/common/ble/ble.mk
index 160e98f..752ab41 100644
--- a/plat/marvell/armada/a8k/common/ble/ble.mk
+++ b/plat/marvell/armada/a8k/common/ble/ble.mk
@@ -21,7 +21,7 @@
 				-I$(CURDIR)/include/lib/libc			\
 				-I$(CURDIR)/include/lib/libc/aarch64
 
-BLE_LINKERFILE		:=	$(BLE_PATH)/ble.ld.S
+BLE_DEFAULT_LINKER_SCRIPT_SOURCE := $(BLE_PATH)/ble.ld.S
 
 BLE_OBJS := $(addprefix $(BUILD_PLAT)/ble/,$(call SOURCES_TO_OBJS,$(BLE_SOURCES)))
 $(BLE_OBJS): PLAT_INCLUDES += -I$(MV_DDR_PATH)