powerpc/maple: Remove obsoleted declaration for maple_calibrate_decr()

The maple_calibrate_decr() have been removed since
commit 10f7e7c1 ("[PATCH] ppc64: consolidate calibrate_decr
implementations"), and now it is useless, so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240822130609.786431-3-cuigaosheng1@huawei.com

arch/powerpc/platforms/maple/maple.h

@@ -7,7 +7,6 @@
 extern int maple_set_rtc_time(struct rtc_time *tm);
 extern void maple_get_rtc_time(struct rtc_time *tm);
 extern time64_t maple_get_boot_time(void);
-extern void maple_calibrate_decr(void);
 extern void maple_pci_init(void);
 extern void maple_pci_irq_fixup(struct pci_dev *dev);
 extern int maple_pci_get_legacy_ide_irq(struct pci_dev *dev, int channel);