Fix rcache data mismatch if lfs->cfg->read() returns an error (non-zero)

[simaodangan]

Description

After a file is successfully opened and written, if the SD card fails (for example, the card is removed), subsequent operations may behave incorrectly.

A simplified example:

file = lfs_open(); // Success

lfs_write(file, "something 1"); // Success

// Simulate SD card removal: lfs->cfg->read() now returns a negative error code

// During the next write, lfs attempts to write to the last block.
// The read operation fails, but rcache still points to the last block.
lfs_write(file, "something 2");   // Fails

// When reading the file and accessing the last block, rcache matches.
// Invalid data is read from rcache, and the return value is "LFS_ERR_OK".
error_code = lfs_read(file, buffer); // Returns "LFS_ERR_OK", but buffer contains invalid data

[geky-bot]

Tests passed ✓, Code: 17208 B (+0.0%), Stack: 1448 B (+0.0%), Structs: 812 B (+0.0%)

	Code	Stack	Structs		Coverage
Default	17208 B (+0.0%)	1448 B (+0.0%)	812 B (+0.0%)	Lines	2450/2611 lines (-0.0%)
Readonly	6242 B (+0.1%)	448 B (+0.0%)	812 B (+0.0%)	Branches	1301/1638 branches (-0.0%)
Threadsafe	18064 B (+0.0%)	1448 B (+0.0%)	820 B (+0.0%)		Benchmarks
Multiversion	17280 B (+0.0%)	1448 B (+0.0%)	816 B (+0.0%)	Readed	29000746676 B (+0.0%)
Migrate	18872 B (+0.0%)	1752 B (+0.0%)	816 B (+0.0%)	Proged	1482895246 B (+0.0%)
Error-asserts	18040 B (+0.0%)	1440 B (+0.0%)	812 B (+0.0%)	Erased	1568921600 B (+0.0%)