[sw] Add MSECCFGH register to CSR library

This CSR represents the high 32 bits of MSECCFG and was added to
Ibex in:

https://github.com/lowRISC/ibex/pull/1310

We should probably autogenerate this list at some point but it
isn't a priority right now.

Signed-off-by: Michael Munday <mike.munday@lowrisc.org>
diff --git a/sw/device/lib/base/csr_registers.h b/sw/device/lib/base/csr_registers.h
index a05ea05..09ef900 100644
--- a/sw/device/lib/base/csr_registers.h
+++ b/sw/device/lib/base/csr_registers.h
@@ -52,6 +52,7 @@
 #define CSR_REG_MTVAL 0x343
 #define CSR_REG_MIP 0x344
 #define CSR_REG_MSECCFG 0x390
+#define CSR_REG_MSECCFGH 0x391
 #define CSR_REG_PMPCFG0 0x3A0
 #define CSR_REG_PMPCFG1 0x3A1
 #define CSR_REG_PMPCFG2 0x3A2