soc/intel: Drop casts around soc_read_pmc_base()

The `soc_read_pmc_base()` function returns an `uintptr_t`, which is then
casted to a pointer type for use with `read32()` and/or `write32()`. But
since commit b324df6a54 (arch/x86: Provide
readXp/writeXp helpers in arch/mmio.h), the `read32p()` and `write32p()`
functions live in `arch/mmio.h`. These functions use the `uintptr_t type
for the address parameter instead of a pointer type, and using them with
the `soc_read_pmc_base()` function allows dropping the casts to pointer.

Change-Id: Iaf16e6f23d139e6f79360d9a29576406b7b15b07
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55840
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>

src/soc/intel/cannonlake/acpi.c

@@ -166,8 +166,7 @@ void soc_fill_fadt(acpi_fadt_t *fadt)
 }
 uint32_t soc_read_sci_irq_select(void)
 {
-	uintptr_t pmc_bar = soc_read_pmc_base();
-	return read32((void *)pmc_bar + IRQ_REG);
+	return read32p(soc_read_pmc_base() + IRQ_REG);
 }
 
 void soc_fill_gnvs(struct global_nvs *gnvs)