images: add vfat support to kernel

Ubuntu cloud images use this for EFI.

images/kernel/config-5.4.46

@@ -2337,8 +2337,12 @@ CONFIG_VIRTIO_FS=y
 #
 # DOS/FAT/NT Filesystems
 #
+CONFIG_FAT_FS=y
 # CONFIG_MSDOS_FS is not set
-# CONFIG_VFAT_FS is not set
+CONFIG_VFAT_FS=y
+CONFIG_FAT_DEFAULT_CODEPAGE=437
+CONFIG_FAT_DEFAULT_IOCHARSET="iso8859-1"
+CONFIG_FAT_DEFAULT_UTF8=y
 # CONFIG_NTFS_FS is not set
 # end of DOS/FAT/NT Filesystems
 
@@ -2389,7 +2393,7 @@ CONFIG_MISC_FILESYSTEMS=y
 # CONFIG_NETWORK_FILESYSTEMS is not set
 CONFIG_NLS=y
 CONFIG_NLS_DEFAULT="iso8859-1"
-# CONFIG_NLS_CODEPAGE_437 is not set
+CONFIG_NLS_CODEPAGE_437=y
 # CONFIG_NLS_CODEPAGE_737 is not set
 # CONFIG_NLS_CODEPAGE_775 is not set
 # CONFIG_NLS_CODEPAGE_850 is not set
@@ -2413,7 +2417,7 @@ CONFIG_NLS_DEFAULT="iso8859-1"
 # CONFIG_NLS_CODEPAGE_1250 is not set
 # CONFIG_NLS_CODEPAGE_1251 is not set
 # CONFIG_NLS_ASCII is not set
-# CONFIG_NLS_ISO8859_1 is not set
+CONFIG_NLS_ISO8859_1=y
 # CONFIG_NLS_ISO8859_2 is not set
 # CONFIG_NLS_ISO8859_3 is not set
 # CONFIG_NLS_ISO8859_4 is not set
@@ -2437,7 +2441,7 @@ CONFIG_NLS_DEFAULT="iso8859-1"
 # CONFIG_NLS_MAC_INUIT is not set
 # CONFIG_NLS_MAC_ROMANIAN is not set
 # CONFIG_NLS_MAC_TURKISH is not set
-# CONFIG_NLS_UTF8 is not set
+CONFIG_NLS_UTF8=y
 # CONFIG_DLM is not set
 # CONFIG_UNICODE is not set
 # end of File systems