staging: fpgaboot: change FPGA indirect article to an

Change use of 'a fpga' to 'an fpga'
Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20210608212350.3029742-13-trix@redhat.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gs_fpgaboot/README

@@ -39,7 +39,7 @@ TABLE OF CONTENTS.
 
 5. USE CASE (from a mailing list discussion with Greg)
 
-	a. As a FPGA development support tool,
+	a. As an FPGA development support tool,
 	During FPGA firmware development, you need to download a new FPGA
 	image frequently.
 	You would do that with a dedicated JTAG, which usually a limited