clk: analogbits: Allow building the library as a module

This library is only used by the SiFive PRCI driver. When that driver is
built as a module, it makes sense to build this library as a module too.

Signed-off-by: Samuel Holland <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/analogbits/Kconfig

···
 # SPDX-License-Identifier: GPL-2.0-only
 config CLK_ANALOGBITS_WRPLL_CLN28HPC
-	bool
+	tristate

drivers/clk/analogbits/wrpll-cln28hpc.c

···
 #include <linux/math64.h>
 #include <linux/math.h>
 #include <linux/minmax.h>
+#include <linux/module.h>
 
 #include <linux/clk/analogbits-wrpll-cln28hpc.h>
 
···
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(wrpll_configure_for_rate);
 
 /**
  * wrpll_calc_output_rate() - calculate the PLL's target output rate
···
 
 	return n;
 }
+EXPORT_SYMBOL_GPL(wrpll_calc_output_rate);
 
 /**
  * wrpll_calc_max_lock_us() - return the time for the PLL to lock
···
 {
 	return MAX_LOCK_US;
 }
+EXPORT_SYMBOL_GPL(wrpll_calc_max_lock_us);
+
+MODULE_AUTHOR("Paul Walmsley <[e-mail]>");
+MODULE_DESCRIPTION("Analog Bits Wide-Range PLL library");
+MODULE_LICENSE("GPL");