sandbox: clk: add clk enable/disable test code

Since we added clk enable_count and prograte clk child enabling
operation to clk parent, so add a new function sandbox_clk_enable_count
to get enable_count for test usage.

And add test code to get the enable_count after we enable/disable
the device clk.

Signed-off-by: Peng Fan <peng.fan@nxp.com>

include/sandbox-clk.h

@@ -20,6 +20,7 @@ enum {
 	SANDBOX_CLK_USDHC1_SEL,
 	SANDBOX_CLK_USDHC2_SEL,
 	SANDBOX_CLK_I2C,
+	SANDBOX_CLK_I2C_ROOT,
 };
 
 enum sandbox_pllv3_type {
@@ -74,4 +75,6 @@ static inline struct clk *sandbox_clk_mux(const char *name, void __iomem *reg,
 				width, 0);
 }
 
+int sandbox_clk_enable_count(struct clk *clk);
+
 #endif /* __SANDBOX_CLK_H__ */