ASoC: Intel: avs: Add missing audio amplifier for KBL

KBL platform is missing the definition of 'max98357a' audio amplifier.
This amplifier is used on many KBL Chromebooks, for instance variant
'nami' of 'Google/poppy' baseboard.
Reported-by: CoolStar <coolstarorganization@gmail.com>
Signed-off-by: Alicja Michalska <ahplka19@gmail.com>

Link: https://lore.kernel.org/r/Y3wHyJ/EcsLRHGr3@toraSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/avs/board_selection.c

@@ -143,6 +143,14 @@ static struct snd_soc_acpi_mach avs_kbl_i2s_machines[] = {
 		},
 		.tplg_filename = "max98373-tplg.bin",
 	},
+	{
+		.id = "MX98357A",
+		.drv_name = "avs_max98357a",
+		.mach_params = {
+			.i2s_link_mask = AVS_SSP(0),
+		},
+		.tplg_filename = "max98357a-tplg.bin",
+	},
 	{
 		.id = "DLGS7219",
 		.drv_name = "avs_da7219",