.gitignore: add SPDX License Identifier

Add SPDX License Identifier to all .gitignore files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

certs/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 x509_certificate_list

drivers/atm/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 fore200e_mkfirm
 fore200e_pca_fw.c
 pca200e.bin

drivers/crypto/vmx/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 aesp8-ppc.S
 ghashp8-ppc.S

drivers/eisa/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 devlist.h

drivers/gpu/drm/i915/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 *.hdrtest

drivers/gpu/drm/radeon/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 mkregtable
 *_reg_safe.h
 

drivers/memory/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 ti-emif-asm-offsets.h

drivers/net/wan/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 wanxlfw.inc

drivers/scsi/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 53c700_d.h
 scsi_devinfo_tbl.c

drivers/scsi/aic7xxx/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 aic79xx_reg.h
 aic79xx_reg_print.c
 aic79xx_seq.h

drivers/staging/comedi/drivers/ni_routing/tools/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 comedi_h.py
 *.pyc
 ni_values.py

drivers/staging/greybus/tools/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 loopback_test

drivers/video/logo/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 *_mono.c
 *_vga16.c
 *_clut224.c

drivers/zorro/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 devlist.h
 gen-devlist

fs/unicode/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 mkutf8data
 utf8data.h

kernel/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 kheaders.md5
 timeconst.h
 hz.bc

kernel/debug/kdb/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 gen-kdb_cmds.c

lib/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 gen_crc32table
 gen_crc64table
 crc32table.h

lib/raid6/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 mktables
 altivec*.c
 int*.c

net/bpfilter/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
 bpfilter_umh