soc/qc/spmi: Add API to read byte array

Introduce a new API, spmi_read_bytes(), to allow reading a
sequence of registers from a Qualcomm PMIC using the SPMI bus.

While the existing spmi_read8() is suitable for single-byte
access, reading large log areas (like the PON history log)
requires iterating over a contiguous block of addresses. This
new function encapsulates the required loop, calling spmi_read8()
sequentially for each address in the range.

This abstraction improves code cleanliness and makes high-level PMIC
log parsing much simpler.

Key changes:
- Define spmi_read_bytes() prototype in qcom_spmi.h.
- Implement spmi_read_bytes() in spmi.c to perform sequential
  reads using spmi_read8().

BUG=b:439819922
TEST=Verify off-mode charging behavior on Google/Quenbi.

Change-Id: I6017336a882a8fa8d771b0127e78dd4f0fdbdd0e
Signed-off-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90191
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/soc/qualcomm/common/include/soc/qcom_spmi.h

@@ -11,5 +11,6 @@
 
 int spmi_read8(uint32_t addr);
 int spmi_write8(uint32_t addr, uint8_t data);
+int spmi_read_bytes(uint32_t addr, uint8_t *data, uint32_t num_bytes);
 
 #endif	// __SOC_QCOM_SPMI_H__

src/soc/qualcomm/common/spmi.c

@@ -125,3 +125,19 @@ int spmi_write8(uint32_t addr, uint8_t data)
 
 	return ret;
 }
+
+int spmi_read_bytes(uint32_t addr, uint8_t *data, uint32_t num_bytes)
+{
+	int spmi_result;
+	if (!data)
+		return -1;
+
+	for (uint32_t i = 0; i < num_bytes; i++) {
+		spmi_result = spmi_read8(addr + i);
+		if (spmi_result < 0)
+			return -1;
+		*data = spmi_result & 0xff;
+		data++;
+	}
+	return 0;
+}