regulator: qcom-smd: make smd_vreg_rpm static

Since smd_vreg_rpm is used only in
drivers/regulator/qcom_smd-regulator.c, make it static and fix the
following sparse warning:

drivers/regulator/qcom_smd-regulator.c:14:21: sparse: warning:
symbol 'smd_vreg_rpm' was not declared. Should it be static?

No functional changes intended.

Fixes: 5df3b41 ("regulator: qcom_smd: Keep one rpm handle for all vregs")
Signed-off-by: Min-Hua Chen <minhuadotchen@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patch.msgid.link/20240926231038.31916-1-minhuadotchen@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Min-Hua

drivers/regulator/qcom_smd-regulator.c

@@ -11,7 +11,7 @@
 #include <linux/regulator/of_regulator.h>
 #include <linux/soc/qcom/smd-rpm.h>
 
-struct qcom_smd_rpm *smd_vreg_rpm;
+static struct qcom_smd_rpm *smd_vreg_rpm;
 
 struct qcom_rpm_reg {
 	struct device *dev;