soc/mediatek/common: Convert mt6359p_read_field() to a general API

Make mt6359p_read_field() a general API usable by multiple drivers,
instead of a static function limited to the original driver.

BUG=b:379008996
BRANCH=none
TEST=build pass

Signed-off-by: Zhigang Qin <zhigang.qin@mediatek.corp-partner.google.com>
Change-Id: I2d9c3de9ad08f918a84fa63c1e9b3af7adc5974a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/87336
Reviewed-by: Yidi Lin <yidilin@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>

src/soc/mediatek/common/include/soc/mt6359p.h

@@ -88,6 +88,7 @@ void mt6359p_enable_vpa(bool enable);
 void mt6359p_enable_vsim1(bool enable);
 void mt6359p_enable_vm18(bool enable);
 void mt6359p_init_pmif_arb(void);
+u32 mt6359p_read_field(u32 reg, u32 mask, u32 shift);
 void mt6359p_write_field(u32 reg, u32 val, u32 mask, u32 shift);
 void mt6359p_init_setting(void);
 void mt6359p_lp_setting(void);

src/soc/mediatek/common/mt6359p.c

@@ -50,7 +50,7 @@ static void mt6359p_write(u32 reg, u32 data)
 	pmif_arb->write(pmif_arb, 0, reg, data);
 }
 
-static u32 mt6359p_read_field(u32 reg, u32 mask, u32 shift)
+u32 mt6359p_read_field(u32 reg, u32 mask, u32 shift)
 {
 	return pmif_arb->read_field(pmif_arb, 0, reg, mask, shift);
 }