Fix FMC read address bounds

The FMC flash end address was off by one, causing boundary checks to reject valid reads at the end of the flash region. This updates the end-of-range calculation to the actual flash limit and adds debug logging around the read validation path.

Author: vanvught

lib-gd32/src/f/fmc/gd32_fmc.cpp

@@ -51,7 +51,7 @@ constexpr auto kBanK1FlashPage = 4 * k1KiB;
 constexpr uint32_t kStartAddress = FLASH_BASE;
 constexpr uint32_t kBank0StartAddress = kStartAddress;
 constexpr uint32_t kBank1StartAddress = 0x08080000;
-const uint32_t kEndAddress = (kStartAddress + (FMC_SIZE * k1KiB) - 1);
+const uint32_t kEndAddress = (kStartAddress + (FMC_SIZE * k1KiB));
 
 enum class State { kIdle, kEraseBusy, kEraseProgram, kWriteBusy, kWriteProgram };
 
@@ -124,9 +124,12 @@ bool Read(uint32_t offset, std::span<uint8_t> buffer) {
     GD32_FMC_DEBUG_ENTRY();
 
     const auto kAddress = offset + FLASH_BASE;
+	
+	GD32_FMC_DEBUG_PRINTF("kStartAddress=%p, kAddress=%p, kEndAddress=%p", reinterpret_cast<void*>(kStartAddress), reinterpret_cast<void*>(kAddress), reinterpret_cast<void*>(kEndAddress));
 
     if (buffer.empty() || ((buffer.size() % sizeof(uint32_t)) != 0) || (kAddress < kStartAddress) || (kAddress >= kEndAddress) || (buffer.size() > (kEndAddress - kAddress))) {
-        return false;
+		GD32_FMC_DEBUG_EXIT();
+		return false;
     }
 
     assert((reinterpret_cast<uintptr_t>(buffer.data()) % alignof(uint32_t)) == 0);