Makefile: Fix typo around CONFIG_SPL_FIT_SOURCE

Trivial fix.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/Makefile b/Makefile
index 1d9ade9..60ae53d 100644
--- a/Makefile
+++ b/Makefile
@@ -1232,7 +1232,7 @@
 CONFIG_SYS_UBOOT_START := 0
 endif
 
-# Boards with more complex image requirments can provide an .its source file
+# Boards with more complex image requirements can provide an .its source file
 # or a generator script
 ifneq ($(CONFIG_SPL_FIT_SOURCE),"")
 U_BOOT_ITS = $(subst ",,$(CONFIG_SPL_FIT_SOURCE))