[NXP][Zephyr] Increase the PSA key slot count to meet Matter requirement (#35811)

Signed-off-by: Axel Le Bourhis <axel.lebourhis@nxp.com>
diff --git a/src/platform/nxp/zephyr/nxp-zephyr-mbedtls-config.h b/src/platform/nxp/zephyr/nxp-zephyr-mbedtls-config.h
index f5f4439..81f1bb7 100644
--- a/src/platform/nxp/zephyr/nxp-zephyr-mbedtls-config.h
+++ b/src/platform/nxp/zephyr/nxp-zephyr-mbedtls-config.h
@@ -18,6 +18,7 @@
 
 #if CONFIG_CHIP_CRYPTO_PSA
 #define MBEDTLS_PSA_CRYPTO_DRIVERS
+#define MBEDTLS_PSA_KEY_SLOT_COUNT 64
 #endif /* CONFIG_CHIP_CRYPTO_PSA */
 
 #if CONFIG_MCUX_ELS_PKC