binman: Remove hard-coded file name for x86 CMC/FSP/VGA

Now that we have added file names from Kconfig in x86 u-boot.dtsi,
update binman to avoid using hard-coded names.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/binman/etype/intel_cmc.py

@@ -12,6 +12,3 @@ from blob import Entry_blob
 class Entry_intel_cmc(Entry_blob):
     def __init__(self, image, etype, node):
         Entry_blob.__init__(self, image, etype, node)
-
-    def GetDefaultFilename(self):
-        return 'cmc.bin'

tools/binman/etype/intel_fsp.py

@@ -12,6 +12,3 @@ from blob import Entry_blob
 class Entry_intel_fsp(Entry_blob):
     def __init__(self, image, etype, node):
         Entry_blob.__init__(self, image, etype, node)
-
-    def GetDefaultFilename(self):
-        return 'fsp.bin'

tools/binman/etype/intel_vga.py

@@ -12,6 +12,3 @@ from blob import Entry_blob
 class Entry_intel_vga(Entry_blob):
     def __init__(self, image, etype, node):
         Entry_blob.__init__(self, image, etype, node)
-
-    def GetDefaultFilename(self):
-        return 'vga.bin'