oberon: Fix re-define of PSA_VENDOR_ECC_MAX_CURVE_BITS

PSA_VENDOR_ECC_MAX_CURVE_BITS gets in already defined in the
autogenerated nrf-config-user.h and if these defines don't match
it results in a redefined warning

Ref: NCSDK-21666

Signed-off-by: Markus Swarowsky <markus.swarowsky@nordicsemi.no>

ext/oberon/psa/core/include/psa/crypto_sizes.h

@@ -196,6 +196,7 @@
 
 /* The maximum size of an ECC key on this implementation, in bits.
  * This is a vendor-specific macro. */
+#ifndef PSA_VENDOR_ECC_MAX_CURVE_BITS
 #if defined(PSA_WANT_ECC_SECP_R1_521)           /*!!OM*/
 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 521
 #elif defined(PSA_WANT_ECC_BRAINPOOL_P_R1_512)
@@ -229,6 +230,7 @@
 #else
 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 0
 #endif
+#endif
 
 /** This macro returns the maximum supported length of the PSK for the
  * TLS-1.2 PSK-to-MS key derivation