Makefile: clean build generated SPL binary for TI AM65x

TI AM65x platforms (evm and HS) generate an SPL image
'tispl.bin*' and there is no rule for cleanup.
Added entry for cleanup in clean target.

Signed-off-by: Suniel Mahesh <sunil.m@techveda.org>
diff --git a/Makefile b/Makefile
index 76f9a72..0570d02 100644
--- a/Makefile
+++ b/Makefile
@@ -1852,7 +1852,7 @@
 		-o -name 'dsdt.aml' -o -name 'dsdt.asl.tmp' -o -name 'dsdt.c' \
 		-o -name '*.efi' -o -name '*.gcno' -o -name '*.so' \) \
 		-type f -print | xargs rm -f \
-		bl31.c bl31.elf bl31_*.bin image.map
+		bl31.c bl31.elf bl31_*.bin image.map tispl.bin*
 
 # mrproper - Delete all generated files, including .config
 #