ipm: imx: Initialize variable before using it

Since the driver is passing the whole buffer, let's zero it to avoid
pass garbage in case of size != buffer's size.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
(cherry picked from commit 98857c267d5825f8b3f3fd1040b7ce222b7f3958)
diff --git a/drivers/ipm/ipm_imx.c b/drivers/ipm/ipm_imx.c
index 511123b..e3de5bd 100644
--- a/drivers/ipm/ipm_imx.c
+++ b/drivers/ipm/ipm_imx.c
@@ -164,7 +164,7 @@
 {
 	const struct imx_mu_config *config = dev->config;
 	MU_Type *base = MU(config);
-	uint32_t data32[IMX_IPM_DATA_REGS];
+	uint32_t data32[IMX_IPM_DATA_REGS] = {0};
 #if !IS_ENABLED(CONFIG_IPM_IMX_REV2)
 	mu_status_t status;
 #endif