Revert "SeaBIOS: Update stable release to 1.15.0"

This reverts commit 2a8de6dafb7eec8ff9112b43888507fbc0d8f851.

SeaBIOS 1.15.0 regresses on systems with NVMe devices [1]:

> Greetings! Was this patch set tested on bare metal hardware? I'm
> seeing "GRUB loading: Read Error" when attempting to boot from NVMe on
> various Purism Librem devices (Intel Skylake thru Cometlake hardware).
> Reverting this series resolves the issue.

So, revert back to SeaBIOS 1.14.0.

[1]: https://mail.coreboot.org/hyperkitty/list/seabios@seabios.org/message/SRECAGH4NE3XPDWJ2YI526L5LPSJWENJ/

Change-Id: If2ec738d478f11b203f499eaa28197357de6630d
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61179
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/payloads/external/SeaBIOS/Kconfig b/payloads/external/SeaBIOS/Kconfig
index 18f2a47..9aea2d0 100644
--- a/payloads/external/SeaBIOS/Kconfig
+++ b/payloads/external/SeaBIOS/Kconfig
@@ -5,7 +5,7 @@
 	default SEABIOS_STABLE
 
 config SEABIOS_STABLE
-	bool "1.15.0"
+	bool "1.14.0"
 	help
 	  Stable SeaBIOS version
 config SEABIOS_MASTER
diff --git a/payloads/external/SeaBIOS/Makefile b/payloads/external/SeaBIOS/Makefile
index d908ba8..cdcd426 100644
--- a/payloads/external/SeaBIOS/Makefile
+++ b/payloads/external/SeaBIOS/Makefile
@@ -1,5 +1,5 @@
 TAG-$(CONFIG_SEABIOS_MASTER)=origin/master
-TAG-$(CONFIG_SEABIOS_STABLE)=2dd4b9b3f84019668719344b40dba79d681be41c
+TAG-$(CONFIG_SEABIOS_STABLE)=155821a1990b6de78dde5f98fa5ab90e802021e0
 TAG-$(CONFIG_SEABIOS_REVISION)=$(CONFIG_SEABIOS_REVISION_ID)
 
 project_git_repo=https://review.coreboot.org/seabios.git