This change addresses a potential out-of-memory access issue in the
devfs filesystem component. The issue arises when the `rt_malloc`
function allocates memory for a path string without accounting for
the null terminator, leading to undefined behavior.
As the manual documented:
> DESCRIPTION
> The strlen() function calculates the length of the string pointed to
> by s, excluding the terminating null byte ('\0').
To fix this, the memory allocation size was increased by one byte
to ensure space for the null terminator. This prevents potential
out-of-memory access and ensures proper string termination.
Signed-off-by: Shell <smokewood@qq.com>