fix(build): restore smbus/smbus_sbs for Linux board targets

The previous commit (6b8fd11) gated smbus and smbus_sbs behind
PX4_PLATFORM=="nuttx" to prevent clang-tidy errors on SITL, but these
libraries depend on device::I2C which has a POSIX implementation
(posix/I2C.cpp). Linux boards like bluerobotics_navigator (armhf) and
emlid_navio2 (aarch64) enable CONFIG_DRIVERS_BATT_SMBUS, which depends
on drivers__smbus — causing CMake to fail with "non-existent target".

Move smbus and smbus_sbs back to unconditional add_subdirectory() so
they are available on all platforms. Keep mcp_common gated behind NuttX
since it includes px4_platform/gpio/mcp.hpp (NuttX-only GPIO headers).

Re-add src/lib/drivers/smbus to the Makefile clang-tidy exclude list
since the SITL compilation database lacks the I2C platform headers
needed for analysis.

Signed-off-by: Ramon Roche <mrpollo@gmail.com>

src/lib/drivers/CMakeLists.txt

@@ -38,8 +38,9 @@ add_subdirectory(led)
 add_subdirectory(magnetometer)
 add_subdirectory(rangefinder)
 
+add_subdirectory(smbus)
+add_subdirectory(smbus_sbs)
+
 if (${PX4_PLATFORM} STREQUAL "nuttx")
 	add_subdirectory(mcp_common)
-	add_subdirectory(smbus)
-	add_subdirectory(smbus_sbs)
 endif()